comms: Comms ought to have better-typed channel recipients

Lewis: May this revision serve well! <did:plc:3fwecdnvtcscjnrx2p4n7alz>

Cargo.lock

@@ -7772,6 +7772,7 @@ dependencies = [
  "tranquil-config",
  "tranquil-db-traits",
  "tranquil-signal",
+ "tranquil-types",
  "uuid",
 ]
 
@@ -8129,6 +8130,7 @@ dependencies = [
  "tokio",
  "tokio-util",
  "tracing",
+ "tranquil-types",
  "url",
  "uuid",
 ]

crates/tranquil-api/src/admin/account/email.rs

@@ -38,7 +38,8 @@ pub async fn send_email(
         .log_db_err("in send_email")?
         .ok_or(ApiError::AccountNotFound)?;
 
-    let email = user.email.ok_or(ApiError::NoEmail)?;
+    let email = tranquil_types::EmailAddress::new(&user.email.ok_or(ApiError::NoEmail)?)
+        .map_err(|e| ApiError::InvalidRequest(e.to_string()))?;
     let (user_id, handle) = (user.id, user.handle);
     let hostname = &tranquil_config::get().server.hostname;
     let subject = input
@@ -50,9 +51,8 @@ pub async fn send_email(
         .infra
         .enqueue_comms(
             Some(user_id),
-            tranquil_db_traits::CommsChannel::Email,
+            &tranquil_types::Recipient::Email(email),
             tranquil_db_traits::CommsType::AdminEmail,
-            &email,
             Some(&subject),
             content,
             None,

crates/tranquil-api/src/admin/account/update.rs

@@ -19,10 +19,10 @@ pub async fn update_account_email(
     Json(input): Json<UpdateAccountEmailInput>,
 ) -> Result<Json<EmptyResponse>, ApiError> {
     let account = input.account.trim();
-    let email = input.email.trim();
-    if account.is_empty() || email.is_empty() {
+    let email = tranquil_types::EmailAddress::new(&input.email)?;
+    if account.is_empty() {
         return Err(ApiError::InvalidRequest(
-            "account and email are required".into(),
+            "Account is required, silly!".into(),
         ));
     }
     let account_did: Did = account
@@ -32,7 +32,7 @@ pub async fn update_account_email(
     match state
         .repos
         .user
-        .admin_update_email(&account_did, email)
+        .admin_update_email(&account_did, &email)
         .await
     {
         Ok(0) => Err(ApiError::AccountNotFound),

crates/tranquil-api/src/common.rs

@@ -1,11 +1,12 @@
 use bcrypt::{DEFAULT_COST, hash};
 use chrono::{DateTime, Utc};
 use std::collections::HashMap;
-use tracing::error;
+use tracing::{error, warn};
 use tranquil_db_traits::{CommsChannel, DidWebOverrides, SessionRepository, UserRepository};
 use tranquil_pds::api::error::ApiError;
 use tranquil_pds::api::error::DbResultExt;
 use tranquil_pds::types::{AtIdentifier, Did, Handle, PasswordHash};
+use tranquil_types::{DiscordUsername, SignalUsername, TelegramUsername};
 
 pub struct ResolvedRepo {
     pub user_id: uuid::Uuid,
@@ -156,42 +157,70 @@ pub struct ChannelInput<'a> {
 pub fn extract_verification_recipient(
     channel: CommsChannel,
     input: &ChannelInput<'_>,
-) -> Result<String, ApiError> {
+) -> Result<tranquil_pds::comms::VerificationTarget, ApiError> {
     match channel {
-        CommsChannel::Email => match input.email {
-            Some(e) if !e.trim().is_empty() => Ok(e.trim().to_string()),
-            _ => Err(ApiError::MissingEmail),
-        },
-        CommsChannel::Discord => match input.discord_username {
-            Some(username) if !username.trim().is_empty() => {
-                let clean = username.trim().to_lowercase();
-                if !tranquil_pds::api::validation::is_valid_discord_username(&clean) {
-                    return Err(ApiError::InvalidRequest(
-                        "Invalid Discord username. Must be 2-32 lowercase characters (letters, numbers, underscores, periods)".into(),
-                    ));
-                }
-                Ok(clean)
-            }
-            _ => Err(ApiError::MissingDiscordId),
-        },
-        CommsChannel::Telegram => match input.telegram_username {
-            Some(username) if !username.trim().is_empty() => {
-                let clean = username.trim().trim_start_matches('@');
-                if !tranquil_pds::api::validation::is_valid_telegram_username(clean) {
-                    return Err(ApiError::InvalidRequest(
-                        "Invalid Telegram username. Must be 5-32 characters, alphanumeric or underscore".into(),
-                    ));
-                }
-                Ok(clean.to_string())
-            }
-            _ => Err(ApiError::MissingTelegramUsername),
-        },
-        CommsChannel::Signal => match input.signal_username {
-            Some(username) if !username.trim().is_empty() => {
-                Ok(username.trim().trim_start_matches('@').to_lowercase())
-            }
-            _ => Err(ApiError::MissingSignalNumber),
-        },
+        CommsChannel::Email => {
+            let raw = trimmed(input.email).ok_or(ApiError::MissingEmail)?;
+            let address = tranquil_types::EmailAddress::new(raw)?;
+            Ok(tranquil_pds::comms::VerificationTarget::direct(
+                tranquil_db_traits::Recipient::Email(address),
+            ))
+        }
+        CommsChannel::Signal => {
+            let raw = trimmed(input.signal_username).ok_or(ApiError::MissingSignalNumber)?;
+            let username = SignalUsername::new(raw)?;
+            Ok(tranquil_pds::comms::VerificationTarget::direct(
+                tranquil_db_traits::Recipient::Signal(username),
+            ))
+        }
+        CommsChannel::Telegram => {
+            let raw = trimmed(input.telegram_username).ok_or(ApiError::MissingTelegramUsername)?;
+            let username = TelegramUsername::new(raw)?;
+            tranquil_pds::comms::VerificationTarget::resolve(
+                channel,
+                username.as_str(),
+                input.email,
+            )
+        }
+        CommsChannel::Discord => {
+            let raw = trimmed(input.discord_username).ok_or(ApiError::MissingDiscordId)?;
+            let username = DiscordUsername::new(raw)?;
+            tranquil_pds::comms::VerificationTarget::resolve(
+                channel,
+                username.as_str(),
+                input.email,
+            )
+        }
+    }
+}
+
+fn trimmed(raw: Option<&str>) -> Option<&str> {
+    raw.map(str::trim).filter(|value| !value.is_empty())
+}
+
+pub async fn implicitly_verify_channel(
+    user_repo: &dyn UserRepository,
+    did: &Did,
+    user_id: uuid::Uuid,
+    preferred_channel: CommsChannel,
+    context: &'static str,
+) {
+    let Ok(Some(prefs)) = user_repo.get_comms_prefs(user_id).await else {
+        return;
+    };
+    let Some(recipient) = tranquil_pds::comms::recipient_for(&prefs, preferred_channel) else {
+        warn!(
+            did = %did,
+            preferred = ?preferred_channel,
+            "We skipped implicit verification on {context} because the account doesn't have a valid recipient"
+        );
+        return;
+    };
+    if let Err(e) = user_repo
+        .set_channel_verified(did, recipient.channel())
+        .await
+    {
+        warn!("Implicit verification on {context} failed: {:?}", e);
     }
 }
 

crates/tranquil-api/src/delegation.rs

@@ -368,8 +368,8 @@ pub async fn create_delegated_account(
         .as_ref()
         .map(|e| e.trim().to_string())
         .filter(|e| !e.is_empty());
-    if let Some(ref email) = email
-        && !tranquil_pds::api::validation::is_valid_email(email)
+    if let Some(email) = &email
+        && tranquil_types::EmailAddress::new(email).is_err()
     {
         return Err(ApiError::InvalidEmail);
     }

crates/tranquil-api/src/discord_webhook.rs

@@ -143,7 +143,20 @@ async fn handle_command(state: AppState, interaction: Interaction) -> Response {
         None => {
             return Json(json!({
                 "type": 4,
-                "data": {"content": "Could not identify user", "flags": 64}
+                "data": {"content": "Couldn't identify user", "flags": 64}
+            }))
+            .into_response();
+        }
+    };
+    let (discord_user_id, discord_username) = match (
+        tranquil_types::DiscordUserId::new(&discord_user_id),
+        tranquil_types::DiscordUsername::new(&discord_username),
+    ) {
+        (Ok(discord_user_id), Ok(discord_username)) => (discord_user_id, discord_username),
+        _ => {
+            return Json(json!({
+                "type": 4,
+                "data": {"content": "Couldn't verify your Discord account", "flags": 64}
             }))
             .into_response();
         }
@@ -184,18 +197,14 @@ async fn handle_command(state: AppState, interaction: Interaction) -> Response {
                 discord_user_id = %discord_user_id,
                 "Verified Discord user and stored user ID"
             );
-            if let Err(e) = comms_repo::enqueue_channel_verified(
+            comms_repo::try_channel_verified_notice(
                 state.repos.user.as_ref(),
                 state.repos.infra.as_ref(),
                 user_id,
-                tranquil_db_traits::CommsChannel::Discord,
-                &discord_user_id,
+                &tranquil_types::Recipient::Discord(discord_user_id),
                 &tranquil_config::get().server.hostname,
             )
-            .await
-            {
-                warn!(error = %e, "Failed to enqueue channel verified notification");
-            }
+            .await;
             Json(json!({
                 "type": 4,
                 "data": {"content": "Verified", "flags": 64}
@@ -299,11 +308,11 @@ mod tests {
     fn parse_handle_whitespace_trimmed() {
         let options = vec![InteractionOption {
             name: "handle".to_string(),
-            value: serde_json::json!("  alice.example.com  "),
+            value: serde_json::json!("  oystercafe.jola.dev  "),
         }];
         assert_eq!(
             parse_start_handle(Some(&options)),
-            Some("alice.example.com".to_string()),
+            Some("oystercafe.jola.dev".to_string()),
         );
     }
 }

crates/tranquil-api/src/identity/account.rs

@@ -51,7 +51,7 @@ async fn try_reactivate_migration(
     handle: &Handle,
     email: &Option<String>,
     verification_channel: tranquil_db_traits::CommsChannel,
-    verification_recipient: Option<&str>,
+    verification_recipient: Option<&tranquil_pds::comms::VerificationTarget>,
 ) -> Option<Response> {
     let reactivate_input = tranquil_db_traits::MigrationReactivationInput {
         did: did.clone(),
@@ -271,8 +271,8 @@ pub async fn create_account(
         .as_ref()
         .map(|e| e.trim().to_string())
         .filter(|e| !e.is_empty());
-    if let Some(ref email) = email
-        && !tranquil_pds::api::validation::is_valid_email(email)
+    if let Some(email) = &email
+        && tranquil_types::EmailAddress::new(email).is_err()
     {
         return ApiError::InvalidEmail.into_response();
     }
@@ -393,7 +393,7 @@ pub async fn create_account(
             &handle,
             &email,
             verification_channel,
-            verification_recipient.as_deref(),
+            verification_recipient.as_ref(),
         )
         .await
     {

crates/tranquil-api/src/identity/plc/request.rs

@@ -35,16 +35,27 @@ pub async fn request_plc_operation_signature(
         .log_db_err("creating PLC token")?;
 
     let hostname = &tranquil_config::get().server.hostname;
-    if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_plc_operation(
+    match tranquil_pds::comms::comms_repo::enqueue_notice(
         state.repos.user.as_ref(),
         state.repos.infra.as_ref(),
         user_id,
-        &display_token,
+        tranquil_pds::comms::Notice::PlcOperation {
+            token: &display_token,
+        },
         hostname,
     )
     .await
     {
-        warn!("Failed to enqueue PLC operation notification: {:?}", e);
+        Ok(Some(_)) => {}
+        Ok(None) => {
+            return Err(ApiError::InvalidRequest(
+                "We couldn't deliver the PLC operation code to your notification channels. Please contact the PDS owner."
+                    .into(),
+            ));
+        }
+        Err(e) => {
+            warn!("Failed to enqueue PLC operation notification: {:?}", e);
+        }
     }
     info!("PLC operation signature requested for user {}", auth.did);
     Ok(Json(EmptyResponse {}))

crates/tranquil-api/src/identity/provision.rs

@@ -315,18 +315,17 @@ pub async fn enqueue_signup_verification(
     user_id: uuid::Uuid,
     did: &Did,
     channel: CommsChannel,
-    recipient: &str,
+    target: &tranquil_pds::comms::VerificationTarget,
 ) {
     let token =
-        tranquil_pds::auth::verification_token::generate_signup_token(did, channel, recipient);
+        tranquil_pds::auth::verification_token::generate_signup_token(did, channel, &target.id);
     let formatted = tranquil_pds::auth::verification_token::format_token_for_display(&token);
     let hostname = &tranquil_config::get().server.hostname;
     if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_signup_verification(
         state.repos.user.as_ref(),
         state.repos.infra.as_ref(),
         user_id,
-        channel,
-        recipient,
+        target,
         &formatted,
         hostname,
     )
@@ -341,18 +340,17 @@ pub async fn enqueue_migration_verification(
     user_id: uuid::Uuid,
     did: &Did,
     channel: CommsChannel,
-    recipient: &str,
+    target: &tranquil_pds::comms::VerificationTarget,
 ) {
     let token =
-        tranquil_pds::auth::verification_token::generate_migration_token(did, channel, recipient);
+        tranquil_pds::auth::verification_token::generate_migration_token(did, channel, &target.id);
     let formatted = tranquil_pds::auth::verification_token::format_token_for_display(&token);
     let hostname = &tranquil_config::get().server.hostname;
     if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_migration_verification(
         state.repos.user.as_ref(),
         state.repos.infra.as_ref(),
         user_id,
-        channel,
-        recipient,
+        target,
         &formatted,
         hostname,
     )

crates/tranquil-api/src/notification_prefs.rs

@@ -159,12 +159,16 @@ pub async fn request_channel_verification(
     user_id: uuid::Uuid,
     did: &Did,
     channel: CommsChannel,
-    identifier: &str,
+    id: &str,
     handle: Option<&Handle>,
 ) -> Result<String, ApiError> {
-    let token = tranquil_pds::auth::verification_token::generate_channel_update_token(
-        did, channel, identifier,
-    );
+    if channel.verifies_via_bot() {
+        return Err(ApiError::InvalidRequest(
+            "This channel verifies through a bot. Please message the bot first so that it's able to reply with useful info".into(),
+        ));
+    }
+    let token =
+        tranquil_pds::auth::verification_token::generate_channel_update_token(did, channel, id);
     let formatted_token = tranquil_pds::auth::verification_token::format_token_for_display(&token);
 
     match channel {
@@ -173,10 +177,11 @@ pub async fn request_channel_verification(
             let handle = handle.ok_or_else(|| {
                 ApiError::InternalError(Some("Email verification requires a handle".into()))
             })?;
+            let new_email = tranquil_types::EmailAddress::new(id)?;
             tranquil_pds::comms::comms_repo::enqueue_email_update(
                 state.repos.infra.as_ref(),
                 user_id,
-                identifier,
+                &new_email,
                 handle,
                 &formatted_token,
                 hostname,
@@ -187,10 +192,10 @@ pub async fn request_channel_verification(
         _ => {
             let hostname = &tranquil_config::get().server.hostname;
             let encoded_token = urlencoding::encode(&formatted_token);
-            let encoded_identifier = urlencoding::encode(identifier);
+            let encoded_id = urlencoding::encode(id);
             let verify_link = format!(
                 "https://{}/app/verify?token={}&identifier={}",
-                hostname, encoded_token, encoded_identifier
+                hostname, encoded_token, encoded_id
             );
             let prefs = state
                 .repos
@@ -212,26 +217,14 @@ pub async fn request_channel_verification(
                 strings.channel_verification_subject,
                 &[("hostname", hostname)],
             );
-            let recipient = match channel {
-                CommsChannel::Telegram => state
-                    .repos
-                    .user
-                    .get_telegram_chat_id(user_id)
-                    .await
-                    .ok()
-                    .flatten()
-                    .map(|id| id.to_string())
-                    .unwrap_or_else(|| identifier.to_string()),
-                _ => identifier.to_string(),
-            };
+            let recipient = tranquil_db_traits::Recipient::new(channel, id)?;
             state
                 .repos
                 .infra
                 .enqueue_comms(
                     Some(user_id),
-                    channel,
-                    tranquil_db_traits::CommsType::ChannelVerification,
                     &recipient,
+                    tranquil_db_traits::CommsType::ChannelVerification,
                     Some(&subject),
                     &body,
                     Some(json!({"code": formatted_token})),
@@ -253,14 +246,7 @@ async fn process_messaging_channel_update(
     effective_channel: CommsChannel,
     verification_required: &mut Vec<CommsChannel>,
 ) -> Result<(), ApiError> {
-    let clean = match channel {
-        CommsChannel::Discord => raw_value.trim().to_lowercase(),
-        CommsChannel::Telegram => raw_value.trim_start_matches('@').to_string(),
-        CommsChannel::Signal => raw_value.trim().trim_start_matches('@').to_lowercase(),
-        CommsChannel::Email => raw_value.trim().to_lowercase(),
-    };
-
-    if clean.is_empty() {
+    if raw_value.trim().is_empty() {
         if effective_channel == channel {
             return Err(ApiError::InvalidRequest(format!(
                 "Cannot remove {:?} while it is the preferred notification channel",
@@ -292,26 +278,12 @@ async fn process_messaging_channel_update(
         return Ok(());
     }
 
-    let valid = match channel {
-        CommsChannel::Discord => tranquil_pds::api::validation::is_valid_discord_username(&clean),
-        CommsChannel::Telegram => tranquil_pds::api::validation::is_valid_telegram_username(&clean),
-        CommsChannel::Signal => tranquil_pds::comms::is_valid_signal_username(&clean),
-        CommsChannel::Email => tranquil_pds::api::validation::is_valid_email(&clean),
+    let clean = match channel {
+        CommsChannel::Discord => tranquil_types::DiscordUsername::new(raw_value)?.to_string(),
+        CommsChannel::Telegram => tranquil_types::TelegramUsername::new(raw_value)?.to_string(),
+        CommsChannel::Signal => tranquil_types::SignalUsername::new(raw_value)?.to_string(),
+        CommsChannel::Email => tranquil_types::EmailAddress::new(raw_value)?.to_string(),
     };
-    if !valid {
-        return Err(match channel {
-            CommsChannel::Discord => ApiError::InvalidRequest(
-                "Invalid Discord username. Must be 2-32 lowercase characters (letters, numbers, underscores, periods)".into(),
-            ),
-            CommsChannel::Telegram => ApiError::InvalidRequest(
-                "Invalid Telegram username. Must be 5-32 characters, alphanumeric or underscore".into(),
-            ),
-            CommsChannel::Signal => ApiError::InvalidRequest(
-                "Invalid Signal username. Must be a 3-32 character nickname, a dot, then a 2-20 digit discriminator".into(),
-            ),
-            CommsChannel::Email => ApiError::InvalidEmail,
-        });
-    }
 
     match channel {
         CommsChannel::Discord => state
@@ -394,23 +366,25 @@ pub async fn update_notification_prefs(
         info!(did = %auth.did, channel = ?effective_channel, "Updated preferred notification channel");
     }
 
-    if let Some(ref new_email) = input.email {
-        let email_clean = new_email.trim().to_lowercase();
-        if email_clean.is_empty() {
-            return Err(ApiError::InvalidRequest("Email cannot be empty".into()));
-        }
+    if let Some(new_email) = &input.email {
+        let email = tranquil_types::EmailAddress::new(new_email).map_err(|_| {
+            if new_email.trim().is_empty() {
+                ApiError::InvalidRequest("Email can't be empty".into())
+            } else {
+                ApiError::InvalidEmail
+            }
+        })?;
 
-        if !tranquil_pds::api::validation::is_valid_email(&email_clean) {
-            return Err(ApiError::InvalidEmail);
-        }
-
-        if current_email.as_ref().map(|e| e.to_lowercase()) != Some(email_clean.clone()) {
+        if !current_email
+            .as_deref()
+            .is_some_and(|e| e.eq_ignore_ascii_case(email.as_str()))
+        {
             request_channel_verification(
                 &state,
                 user_id,
                 &auth.did,
                 CommsChannel::Email,
-                &email_clean,
+                email.as_str(),
                 Some(&handle),
             )
             .await?;

crates/tranquil-api/src/server/account_status.rs

@@ -586,16 +586,27 @@ pub async fn request_account_delete(
         .await
         .log_db_err("creating deletion token")?;
     let hostname = &tranquil_config::get().server.hostname;
-    if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_account_deletion(
+    match tranquil_pds::comms::comms_repo::enqueue_notice(
         state.repos.user.as_ref(),
         state.repos.infra.as_ref(),
         user_id,
-        &confirmation_token,
+        tranquil_pds::comms::Notice::AccountDeletion {
+            code: &confirmation_token,
+        },
         hostname,
     )
     .await
     {
-        warn!("Failed to enqueue account deletion notification: {:?}", e);
+        Ok(Some(_)) => {}
+        Ok(None) => {
+            return Err(ApiError::InvalidRequest(
+                "We couldn't deliver the deletion code to your notification channels. Please contact the PDS owner."
+                    .into(),
+            ));
+        }
+        Err(e) => {
+            warn!("Failed to enqueue account deletion notification: {:?}", e);
+        }
     }
     info!("Account deletion requested for user {}", session_mfa.did());
     Ok(Json(EmptyResponse {}))

crates/tranquil-api/src/server/email.rs

@@ -71,7 +71,7 @@ pub async fn request_email_update(
 
     let Some(_current_email) = user.email else {
         return Err(ApiError::InvalidRequest(
-            "account does not have an email address".into(),
+            "Account doesn't have an email address".into(),
         ));
     };
 
@@ -89,36 +89,43 @@ pub async fn request_email_update(
             ApiError::InternalError(Some("Failed to generate verification code".into()))
         })?;
 
-        if let Some(Json(ref inp)) = input
-            && let Some(ref new_email) = inp.new_email
+        if let Some(Json(inp)) = &input
+            && let Some(new_email) = inp.new_email.as_deref()
+            && let Ok(address) = tranquil_types::EmailAddress::new(new_email)
         {
-            let new_email = new_email.trim().to_lowercase();
-            if !new_email.is_empty() && tranquil_pds::api::validation::is_valid_email(&new_email) {
-                let pending = PendingEmailUpdate {
-                    new_email,
-                    token_hash: hash_token(&token),
-                    authorized: false,
-                };
-                if let Ok(json) = serde_json::to_string(&pending) {
-                    let cache_key = tranquil_pds::cache_keys::email_update_key(&auth.did);
-                    if let Err(e) = state.cache.set(&cache_key, &json, EMAIL_UPDATE_TTL).await {
-                        warn!("Failed to cache pending email update: {:?}", e);
-                    }
-                }
+            let pending = PendingEmailUpdate {
+                new_email: address.as_str().to_string(),
+                token_hash: hash_token(&token),
+                authorized: false,
+            };
+            let cache_key = tranquil_pds::cache_keys::email_update_key(&auth.did);
+            if let Ok(json) = serde_json::to_string(&pending)
+                && let Err(e) = state.cache.set(&cache_key, &json, EMAIL_UPDATE_TTL).await
+            {
+                warn!("Failed to cache pending email update: {:?}", e);
             }
         }
 
         let hostname = &tranquil_config::get().server.hostname;
-        if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_short_token_email(
+        match tranquil_pds::comms::comms_repo::enqueue_notice(
             state.repos.user.as_ref(),
             state.repos.infra.as_ref(),
             user.id,
-            &token,
+            tranquil_pds::comms::Notice::ShortTokenEmail { token: &token },
             hostname,
         )
         .await
         {
-            warn!("Failed to enqueue email update notification: {:?}", e);
+            Ok(Some(_)) => {}
+            Ok(None) => {
+                return Err(ApiError::InvalidRequest(
+                    "We couldn't deliver the confirmation code to your notification channels. Please contact the PDS owner."
+                        .into(),
+                ));
+            }
+            Err(e) => {
+                warn!("Failed to enqueue email update notification: {:?}", e);
+            }
         }
     }
 
@@ -150,13 +157,11 @@ pub async fn confirm_email(
         .log_db_err("getting email info")?
         .ok_or(ApiError::AccountNotFound)?;
 
-    let Some(ref email) = user.email else {
+    let Some(email) = &user.email else {
         return Err(ApiError::InvalidEmail);
     };
-    let current_email = email.to_lowercase();
-
-    let provided_email = input.email.trim().to_lowercase();
-    if provided_email != current_email {
+    let provided_email = tranquil_types::EmailAddress::new(input.email.trim())?;
+    if provided_email.as_str() != email.to_lowercase() {
         return Err(ApiError::InvalidEmail);
     }
 
@@ -170,7 +175,7 @@ pub async fn confirm_email(
     let verified = tranquil_pds::auth::verification_token::verify_signup_token(
         &confirmation_code,
         CommsChannel::Email,
-        &provided_email,
+        provided_email.as_str(),
     );
 
     match verified {
@@ -226,17 +231,14 @@ pub async fn update_email(
     let user_id = user.id;
     let current_email = user.email.clone();
     let email_verified = user.email_verified;
-    let new_email = input.email.trim().to_lowercase();
-
-    if !tranquil_pds::api::validation::is_valid_email(&new_email) {
-        return Err(ApiError::InvalidRequest(
+    let new_email = tranquil_types::EmailAddress::new(input.email.trim()).map_err(|_| {
+        ApiError::InvalidRequest(
             "This email address is not supported, please use a different email.".into(),
-        ));
-    }
-
+        )
+    })?;
     let email_unchanged = current_email
         .as_ref()
-        .map(|c| new_email == c.to_lowercase())
+        .map(|c| new_email.as_str() == c.to_lowercase())
         .unwrap_or(false);
 
     if email_unchanged {
@@ -283,7 +285,7 @@ pub async fn update_email(
         if let Some(pending_json) = state.cache.get(&cache_key).await
             && let Ok(pending) = serde_json::from_str::<PendingEmailUpdate>(&pending_json)
             && pending.authorized
-            && pending.new_email == new_email
+            && pending.new_email == new_email.as_str()
         {
             authorized_via_link = true;
             let _ = state.cache.delete(&cache_key).await;
@@ -350,24 +352,26 @@ pub async fn update_email(
     state
         .repos
         .user
-        .update_email(user_id, &new_email)
+        .update_email(user_id, new_email.as_str())
         .await
         .log_db_err("updating email")?;
 
     let verification_token = tranquil_pds::auth::verification_token::generate_signup_token(
         did,
         CommsChannel::Email,
-        &new_email,
+        new_email.as_str(),
     );
     let formatted_token =
         tranquil_pds::auth::verification_token::format_token_for_display(&verification_token);
     let hostname = &tranquil_config::get().server.hostname;
+    let target = tranquil_pds::comms::VerificationTarget::direct(
+        tranquil_db_traits::Recipient::Email(new_email.clone()),
+    );
     if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_signup_verification(
         state.repos.user.as_ref(),
         state.repos.infra.as_ref(),
         user_id,
-        tranquil_db_traits::CommsChannel::Email,
-        &new_email,
+        &target,
         &formatted_token,
         hostname,
     )
@@ -565,15 +569,22 @@ pub async fn check_email_in_use(
     _rate_limit: RateLimited<VerificationCheckLimit>,
     Json(input): Json<CheckEmailInUseInput>,
 ) -> Result<Json<InUseOutput>, ApiError> {
-    let email = input.email.trim().to_lowercase();
-    if email.is_empty() {
-        return Err(ApiError::InvalidRequest("email is required".into()));
-    }
+    let raw = input.email.trim();
+    let email = tranquil_types::EmailAddress::new(raw).map_err(|_| {
+        ApiError::InvalidRequest(
+            if raw.is_empty() {
+                "Email is required"
+            } else {
+                "Invalid email address"
+            }
+            .into(),
+        )
+    })?;
 
     let count = state
         .repos
         .user
-        .count_accounts_by_email(&email)
+        .count_accounts_by_email(email.as_str())
         .await
         .map_err(|e| {
             error!("DB error checking email usage: {:?}", e);

crates/tranquil-api/src/server/passkey_account.rs

@@ -116,8 +116,8 @@ pub async fn create_passkey_account(
         .as_ref()
         .map(|e| e.trim().to_string())
         .filter(|e| !e.is_empty());
-    if let Some(ref email) = email
-        && !tranquil_pds::api::validation::is_valid_email(email)
+    if let Some(email) = &email
+        && tranquil_types::EmailAddress::new(email).is_err()
     {
         return Err(ApiError::InvalidEmail);
     }
@@ -703,11 +703,11 @@ pub async fn request_passkey_recovery(
         urlencoding::encode(&recovery_token)
     );
 
-    let _ = tranquil_pds::comms::comms_repo::enqueue_passkey_recovery(
+    let _ = tranquil_pds::comms::comms_repo::enqueue_notice(
         state.repos.user.as_ref(),
         state.repos.infra.as_ref(),
         user.id,
-        &recovery_url,
+        tranquil_pds::comms::Notice::PasskeyRecovery { url: &recovery_url },
         hostname,
     )
     .await;
@@ -776,21 +776,14 @@ pub async fn recover_passkey_account(
     if result.passkeys_deleted > 0 {
         info!(did = %input.did, count = result.passkeys_deleted, "Deleted lost passkeys during account recovery");
     }
-    if let Ok(Some(prefs)) = state.repos.user.get_comms_prefs(user.id).await {
-        let actual_channel =
-            tranquil_pds::comms::resolve_delivery_channel(&prefs, user.preferred_comms_channel);
-        if let Err(e) = state
-            .repos
-            .user
-            .set_channel_verified(&input.did, actual_channel)
-            .await
-        {
-            warn!(
-                "Failed to implicitly verify channel on passkey recovery: {:?}",
-                e
-            );
-        }
-    }
+    crate::common::implicitly_verify_channel(
+        state.repos.user.as_ref(),
+        &input.did,
+        user.id,
+        user.preferred_comms_channel,
+        "passkey recovery",
+    )
+    .await;
     info!(did = %input.did, "Passkey-only account recovered with temporary password");
     Ok(Json(SuccessResponse { success: true }))
 }

crates/tranquil-api/src/server/password.rs

@@ -90,11 +90,13 @@ pub async fn request_password_reset(
         return Err(ApiError::InternalError(None));
     }
     let hostname = &tranquil_config::get().server.hostname;
-    if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_password_reset(
+    if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_notice(
         state.repos.user.as_ref(),
         state.repos.infra.as_ref(),
         user_id,
-        &display_code,
+        tranquil_pds::comms::Notice::PasswordReset {
+            code: &display_code,
+        },
         hostname,
     )
     .await
@@ -193,21 +195,14 @@ pub async fn reset_password(
         }
     }))
     .await;
-    if let Ok(Some(prefs)) = state.repos.user.get_comms_prefs(user_id).await {
-        let actual_channel =
-            tranquil_pds::comms::resolve_delivery_channel(&prefs, user.preferred_comms_channel);
-        if let Err(e) = state
-            .repos
-            .user
-            .set_channel_verified(&user.did, actual_channel)
-            .await
-        {
-            warn!(
-                "Failed to implicitly verify channel on password reset: {:?}",
-                e
-            );
-        }
-    }
+    crate::common::implicitly_verify_channel(
+        state.repos.user.as_ref(),
+        &user.did,
+        user_id,
+        user.preferred_comms_channel,
+        "password reset",
+    )
+    .await;
     info!("Password reset completed for user {}", user_id);
     Ok(Json(EmptyResponse {}))
 }

crates/tranquil-api/src/server/session.rs

@@ -220,21 +220,34 @@ pub async fn create_session(
         }
         Ok(tranquil_pds::auth::legacy_2fa::Legacy2faOutcome::ChallengeSent(code)) => {
             let hostname = &tranquil_config::get().server.hostname;
-            if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_2fa_code(
+            match tranquil_pds::comms::comms_repo::enqueue_notice(
                 state.repos.user.as_ref(),
                 state.repos.infra.as_ref(),
                 row.id,
-                code.as_str(),
+                tranquil_pds::comms::Notice::TwoFactorCode {
+                    code: code.as_str(),
+                },
                 hostname,
             )
             .await
             {
-                error!("Failed to send 2FA code: {:?}", e);
-                tranquil_pds::auth::legacy_2fa::clear_challenge(state.cache.as_ref(), &row.did)
-                    .await;
-                return Err(ApiError::InternalError(Some(
-                    "Failed to send verification code. Please try again.".into(),
-                )));
+                Ok(Some(_)) => {}
+                Ok(None) => {
+                    tranquil_pds::auth::legacy_2fa::clear_challenge(state.cache.as_ref(), &row.did)
+                        .await;
+                    return Err(ApiError::InvalidRequest(
+                        "We couldn't deliver the verification code to your notification channels. Please contact the PDS owner."
+                            .into(),
+                    ));
+                }
+                Err(e) => {
+                    error!("Failed to send 2FA code: {:?}", e);
+                    tranquil_pds::auth::legacy_2fa::clear_challenge(state.cache.as_ref(), &row.did)
+                        .await;
+                    return Err(ApiError::InternalError(Some(
+                        "Failed to send verification code. Please try again.".into(),
+                    )));
+                }
             }
             return Err(ApiError::AuthFactorTokenRequired);
         }
@@ -336,13 +349,15 @@ pub async fn create_session(
                 "Legacy login on TOTP-enabled account - sending notification"
             );
             let hostname = &tranquil_config::get().server.hostname;
-            if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_legacy_login(
+            if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_notice(
                 state.repos.user.as_ref(),
                 state.repos.infra.as_ref(),
                 row.id,
+                tranquil_pds::comms::Notice::LegacyLoginAlert {
+                    channel: row.preferred_comms_channel,
+                    ip: client_ip,
+                },
                 hostname,
-                client_ip,
-                row.preferred_comms_channel,
             )
             .await
             {
@@ -868,15 +883,13 @@ pub async fn confirm_signup(
         }
     };
 
-    let identifier = match row.channel {
-        tranquil_db_traits::CommsChannel::Email => row.email.clone().unwrap_or_default(),
-        tranquil_db_traits::CommsChannel::Discord => {
-            row.discord_username.clone().unwrap_or_default()
-        }
-        tranquil_db_traits::CommsChannel::Telegram => {
-            row.telegram_username.clone().unwrap_or_default()
-        }
-        tranquil_db_traits::CommsChannel::Signal => row.signal_username.clone().unwrap_or_default(),
+    let Some(id) = row.channel_identifier() else {
+        warn!(
+            did = %input.did,
+            channel = ?row.channel,
+            "We can't confirm signup because the account doesn't have an identifier on file"
+        );
+        return Err(ApiError::InvalidRequest("Invalid verification code".into()));
     };
 
     let normalized_token =
@@ -884,7 +897,7 @@ pub async fn confirm_signup(
     match tranquil_pds::auth::verification_token::verify_signup_token(
         &normalized_token,
         row.channel,
-        &identifier,
+        id,
     ) {
         Ok(token_data) => {
             if token_data.did != input.did {
@@ -940,10 +953,11 @@ pub async fn confirm_signup(
     };
 
     let hostname = &tranquil_config::get().server.hostname;
-    if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_welcome(
+    if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_notice(
         state.repos.user.as_ref(),
         state.repos.infra.as_ref(),
         row.id,
+        tranquil_pds::comms::Notice::Welcome,
         hostname,
     )
     .await
@@ -962,6 +976,35 @@ pub async fn confirm_signup(
     }))
 }
 
+async fn resend_signup_verification(
+    state: &AppState,
+    row: &tranquil_db_traits::UserResendVerification,
+    did: &Did,
+    context: &'static str,
+) -> bool {
+    let Some(id) = row.channel_identifier() else {
+        warn!(did = %did, channel = ?row.channel, "We skipped {context} because the account doesn't have a recipient on file");
+        return false;
+    };
+    match tranquil_pds::comms::VerificationTarget::resolve(row.channel, id, row.email.as_deref()) {
+        Ok(target) => {
+            crate::identity::provision::enqueue_signup_verification(
+                state,
+                row.id,
+                did,
+                row.channel,
+                &target,
+            )
+            .await;
+            true
+        }
+        Err(_) => {
+            warn!(did = %did, channel = ?row.channel, "We skipped {context} because the account doesn't have a valid recipient");
+            false
+        }
+    }
+}
+
 const AUTO_VERIFY_DEBOUNCE: std::time::Duration = std::time::Duration::from_secs(120);
 
 pub struct AutoResendResult {
@@ -990,37 +1033,15 @@ pub async fn auto_resend_verification(state: &AppState, did: &Did) -> Option<Aut
         handle: row.handle.clone(),
         channel: row.channel,
     };
-    let is_bot_channel = matches!(
-        row.channel,
-        tranquil_db_traits::CommsChannel::Telegram | tranquil_db_traits::CommsChannel::Discord
-    );
-    if is_bot_channel || debounced {
+    if row.channel.verifies_via_bot() || debounced {
         return Some(result);
     }
-    let recipient = match row.channel {
-        tranquil_db_traits::CommsChannel::Email => row.email.clone().unwrap_or_default(),
-        tranquil_db_traits::CommsChannel::Signal => row.signal_username.clone().unwrap_or_default(),
-        _ => return Some(result),
-    };
-    if recipient.is_empty() {
-        warn!(
-            "No recipient configured for auto-resend verification: {}",
-            did
-        );
-        return Some(result);
+    if resend_signup_verification(state, &row, did, "auto-resend verification").await {
+        let _ = state
+            .cache
+            .set(&debounce_key, "1", AUTO_VERIFY_DEBOUNCE)
+            .await;
     }
-    crate::identity::provision::enqueue_signup_verification(
-        state,
-        row.id,
-        did,
-        row.channel,
-        &recipient,
-    )
-    .await;
-    let _ = state
-        .cache
-        .set(&debounce_key, "1", AUTO_VERIFY_DEBOUNCE)
-        .await;
     Some(result)
 }
 
@@ -1050,32 +1071,12 @@ pub async fn resend_verification(
             return Err(ApiError::InternalError(None));
         }
     };
-    let is_verified = row.channel_verification.has_any_verified();
-    if is_verified {
+    if row.channel_verification.has_any_verified() {
         return Err(ApiError::InvalidRequest(
             "Account is already verified".into(),
         ));
     }
-
-    let recipient = match row.channel {
-        tranquil_db_traits::CommsChannel::Email => row.email.clone().unwrap_or_default(),
-        tranquil_db_traits::CommsChannel::Discord => {
-            row.discord_username.clone().unwrap_or_default()
-        }
-        tranquil_db_traits::CommsChannel::Telegram => {
-            row.telegram_username.clone().unwrap_or_default()
-        }
-        tranquil_db_traits::CommsChannel::Signal => row.signal_username.clone().unwrap_or_default(),
-    };
-
-    crate::identity::provision::enqueue_signup_verification(
-        &state,
-        row.id,
-        &input.did,
-        row.channel,
-        &recipient,
-    )
-    .await;
+    resend_signup_verification(&state, &row, &input.did, "resend verification").await;
     Ok(Json(SuccessResponse { success: true }))
 }
 

crates/tranquil-api/src/server/verify_email.rs

@@ -57,9 +57,9 @@ pub async fn resend_migration_verification(
     let channel = input
         .channel
         .unwrap_or(tranquil_db_traits::CommsChannel::Email);
-    let identifier = input.identifier.trim().to_lowercase();
+    let id = input.identifier.trim().to_lowercase();
 
-    let user = match state.repos.user.get_by_email(&identifier).await {
+    let user = match state.repos.user.get_by_email(&id).await {
         Ok(Some(u)) => u,
         Ok(None) => {
             return Ok(Json(ResendMigrationVerificationOutput { sent: true }));
@@ -73,15 +73,18 @@ pub async fn resend_migration_verification(
     if user.email_verified {
         return Ok(Json(ResendMigrationVerificationOutput { sent: true }));
     }
-
-    crate::identity::provision::enqueue_migration_verification(
-        &state,
-        user.id,
-        &user.did,
-        channel,
-        &identifier,
-    )
-    .await;
+    let target = tranquil_pds::comms::VerificationTarget::resolve(channel, &id, Some(&id)).ok();
+    if let Some(target) = target {
+        crate::identity::provision::enqueue_migration_verification(
+            &state, user.id, &user.did, channel, &target,
+        )
+        .await;
+    } else {
+        warn!(
+            channel = ?channel,
+            "We skipped migration verification because unfortunately the account doesn't have a valid recipient"
+        );
+    }
 
     info!(did = %user.did, channel = ?channel, "Resent migration verification");
 

crates/tranquil-api/src/server/verify_token.rs

@@ -66,8 +66,7 @@ pub async fn verify_token_internal(
             handle_channel_update(state, &token_data.did, token_data.channel, &identifier).await
         }
         VerificationPurpose::Signup => {
-            handle_signup_verification(state, &token_data.did, token_data.channel, &identifier)
-                .await
+            handle_signup_verification(state, &token_data.did, token_data.channel).await
         }
     }
 }
@@ -167,7 +166,7 @@ async fn handle_channel_update(
 
     info!(did = %did, channel = ?channel, "Channel verified successfully");
 
-    notify_channel_verified(state, user_id, channel, identifier).await;
+    notify_channel_verified(state, user_id, channel).await;
 
     Ok(Json(VerifyTokenOutput {
         success: true,
@@ -177,43 +176,49 @@ async fn handle_channel_update(
     }))
 }
 
-async fn notify_channel_verified(
-    state: &AppState,
-    user_id: uuid::Uuid,
-    channel: CommsChannel,
-    identifier: &str,
-) {
-    let recipient = match channel {
-        CommsChannel::Telegram => state
-            .repos
-            .user
-            .get_telegram_chat_id(user_id)
-            .await
-            .ok()
-            .flatten()
-            .map(|id| id.to_string())
-            .unwrap_or_else(|| identifier.to_string()),
-        _ => identifier.to_string(),
+async fn notify_channel_verified(state: &AppState, user_id: uuid::Uuid, channel: CommsChannel) {
+    let prefs = match state.repos.user.get_comms_prefs(user_id).await {
+        Ok(Some(prefs)) => prefs,
+        Ok(None) => {
+            warn!(
+                user_id = %user_id,
+                channel = ?channel,
+                "We skipped channel-verified notice because the account doesn't have comms preferences"
+            );
+            return;
+        }
+        Err(e) => {
+            warn!(
+                user_id = %user_id,
+                channel = ?channel,
+                error = ?e,
+                "We skipped channel-verified notice because we couldn't load the account's comms preferences"
+            );
+            return;
+        }
     };
-    if let Err(e) = comms_repo::enqueue_channel_verified(
+    let Some(recipient) = tranquil_pds::comms::recipient_for(&prefs, channel) else {
+        warn!(
+            user_id = %user_id,
+            channel = ?channel,
+            "We skipped channel-verified notice because the account doesn't have a valid recipient"
+        );
+        return;
+    };
+    comms_repo::try_channel_verified_notice(
         state.repos.user.as_ref(),
         state.repos.infra.as_ref(),
         user_id,
-        channel,
         &recipient,
         &tranquil_config::get().server.hostname,
     )
-    .await
-    {
-        warn!(error = %e, "Failed to enqueue channel verified notification");
-    }
+    .await;
 }
 
 async fn handle_signup_verification(
     state: &AppState,
     did: &Did,
     channel: CommsChannel,
-    identifier: &str,
 ) -> Result<Json<VerifyTokenOutput>, ApiError> {
     let user = state
         .repos
@@ -238,7 +243,7 @@ async fn handle_signup_verification(
 
     info!(did = %did, channel = ?channel, "Signup verified successfully");
 
-    notify_channel_verified(state, user.id, channel, identifier).await;
+    notify_channel_verified(state, user.id, channel).await;
 
     Ok(Json(VerifyTokenOutput {
         success: true,

crates/tranquil-api/src/telegram_webhook.rs

@@ -76,6 +76,13 @@ pub async fn handle_telegram_webhook(
                     return StatusCode::OK;
                 }
             };
+            let username = match tranquil_types::TelegramUsername::new(username) {
+                Ok(username) => username,
+                Err(e) => {
+                    warn!(error = %e, "We ignored a /start with an invalid Telegram username");
+                    return StatusCode::OK;
+                }
+            };
 
             debug!(
                 telegram_username = %username,
@@ -95,17 +102,21 @@ pub async fn handle_telegram_webhook(
                         chat_id = from.id,
                         "Verified Telegram user and stored chat_id"
                     );
-                    if let Err(e) = comms_repo::enqueue_channel_verified(
-                        state.repos.user.as_ref(),
-                        state.repos.infra.as_ref(),
-                        user_id,
-                        tranquil_db_traits::CommsChannel::Telegram,
-                        &from.id.to_string(),
-                        &tranquil_config::get().server.hostname,
-                    )
-                    .await
-                    {
-                        warn!(error = %e, "Failed to enqueue channel verified notification");
+                    match tranquil_types::TelegramChatId::from_i64(from.id) {
+                        Some(chat_id) => {
+                            comms_repo::try_channel_verified_notice(
+                                state.repos.user.as_ref(),
+                                state.repos.infra.as_ref(),
+                                user_id,
+                                &tranquil_types::Recipient::Telegram(chat_id),
+                                &tranquil_config::get().server.hostname,
+                            )
+                            .await;
+                        }
+                        None => warn!(
+                            chat_id = from.id,
+                            "We skipped verified notice because the Telegram chat ID can't be 0"
+                        ),
                     }
                 }
                 Ok(None) => {
@@ -178,8 +189,8 @@ mod tests {
     #[test]
     fn payload_with_extra_whitespace_trimmed() {
         assert_eq!(
-            parse_start_handle(Some("/start  alice_example_com  ")),
-            Some("alice.example.com".to_string()),
+            parse_start_handle(Some("/start  oys_nel_pet  ")),
+            Some("oys.nel.pet".to_string()),
         );
     }
 }

crates/tranquil-comms/Cargo.toml

@@ -7,6 +7,7 @@ license.workspace = true
 [dependencies]
 tranquil-config = { workspace = true }
 tranquil-signal = { workspace = true }
+tranquil-types = { workspace = true }
 
 async-trait = { workspace = true }
 base64 = { workspace = true }

crates/tranquil-comms/src/email/message.rs

@@ -6,15 +6,16 @@ use uuid::Uuid;
 
 use super::types::EmailDomain;
 use crate::sender::SendError;
-use crate::types::{CommsType, QueuedComms};
+use crate::{CommsType, QueuedComms};
 
 pub(super) fn build(
     from: &Mailbox,
     qc: &QueuedComms,
+    to: &tranquil_types::EmailAddress,
     apply_atmos_categories: bool,
 ) -> Result<Message, SendError> {
-    let to: Mailbox = qc
-        .recipient
+    let to: Mailbox = to
+        .as_str()
         .parse()
         .map_err(|e: lettre::address::AddressError| SendError::InvalidRecipient(e.to_string()))?;
     let subject = qc.subject.as_deref().unwrap_or("Notification");
@@ -101,7 +102,7 @@ fn atmos_category(comms_type: CommsType) -> Option<AtmosCategory> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::types::{CommsChannel, CommsStatus};
+    use crate::{CommsChannel, CommsStatus};
     use chrono::Utc;
     use uuid::Uuid;
 
@@ -109,6 +110,10 @@ mod tests {
         "Test Sender <noreply@nel.pet>".parse().unwrap()
     }
 
+    fn to(recipient: &str) -> tranquil_types::EmailAddress {
+        tranquil_types::EmailAddress::new(recipient).unwrap()
+    }
+
     fn fixture(recipient: &str, subject: Option<&str>, body: &str) -> QueuedComms {
         QueuedComms {
             id: Uuid::new_v4(),
@@ -135,6 +140,7 @@ mod tests {
         let msg = build(
             &from_mailbox(),
             &fixture("user@nel.pet", Some("Welcome"), "Hello world."),
+            &to("user@nel.pet"),
             false,
         )
         .unwrap();
@@ -153,6 +159,7 @@ mod tests {
         let msg = build(
             &from_mailbox(),
             &fixture("user@nel.pet", Some("héllo wörld"), "Body"),
+            &to("user@jola.dev"),
             false,
         )
         .unwrap();
@@ -163,12 +170,8 @@ mod tests {
 
     #[test]
     fn header_injection_rejected() {
-        let result = build(
-            &from_mailbox(),
-            &fixture("x@nel.pet\r\nBcc: evil@x", Some("s"), "b"),
-            false,
-        );
-        assert!(matches!(result, Err(SendError::InvalidRecipient(_))));
+        let result = tranquil_types::EmailAddress::new("x@jola.dev\r\nBcc: evil@x");
+        assert!(result.is_err());
     }
 
     #[test]
@@ -176,13 +179,14 @@ mod tests {
         let msg = build(
             &from_mailbox(),
             &fixture("user@nel.pet", Some("hi\r\nBcc: evil@nel.pet"), "body"),
+            &to("user@jola.dev"),
             false,
         )
         .expect("subject CRLF should be encoded, not rejected");
         let raw = String::from_utf8(msg.formatted()).unwrap();
         assert!(
             !raw.contains("Bcc:"),
-            "CRLF in subject must not produce a Bcc header: {raw}"
+            "CRLF in subject mustn't produce a Bcc header: {raw}"
         );
         assert!(
             raw.contains("Subject: ="),
@@ -195,6 +199,7 @@ mod tests {
         let msg = build(
             &from_mailbox(),
             &fixture("user@nel.pet", Some("s"), "b"),
+            &to("user@jola.dev"),
             false,
         )
         .unwrap();
@@ -214,6 +219,7 @@ mod tests {
         let msg = build(
             &from_mailbox(),
             &fixture("user@nel.pet", None, "Body"),
+            &to("user@nel.pet"),
             false,
         )
         .unwrap();
@@ -226,6 +232,7 @@ mod tests {
         let msg = build(
             &from_mailbox(),
             &fixture("user@Nel.PET", Some("s"), "b"),
+            &to("user@nel.pet"),
             false,
         )
         .unwrap();
@@ -239,7 +246,7 @@ mod tests {
             comms_type: CommsType::PasswordReset,
             ..fixture("user@nel.pet", Some("s"), "b")
         };
-        let msg = build(&from_mailbox(), &qc, true).unwrap();
+        let msg = build(&from_mailbox(), &qc, &to("user@jola.dev"), true).unwrap();
         let raw = String::from_utf8(msg.formatted()).unwrap();
         assert!(raw.contains("X-Atmos-Category: password-reset"));
     }
@@ -250,7 +257,7 @@ mod tests {
             comms_type: CommsType::PasswordReset,
             ..fixture("user@nel.pet", Some("s"), "b")
         };
-        let msg = build(&from_mailbox(), &qc, false).unwrap();
+        let msg = build(&from_mailbox(), &qc, &to("user@nel.pet"), false).unwrap();
         let raw = String::from_utf8(msg.formatted()).unwrap();
         assert!(!raw.contains("X-Atmos-Category"));
     }
@@ -261,7 +268,7 @@ mod tests {
             comms_type: CommsType::AdminEmail,
             ..fixture("user@nel.pet", Some("s"), "b")
         };
-        let msg = build(&from_mailbox(), &qc, true).unwrap();
+        let msg = build(&from_mailbox(), &qc, &to("user@nel.pet"), true).unwrap();
         let raw = String::from_utf8(msg.formatted()).unwrap();
         assert!(!raw.contains("X-Atmos-Category"));
     }

crates/tranquil-comms/src/email/mod.rs

@@ -25,7 +25,7 @@ use self::types::{
     SmtpUsername, TlsMode,
 };
 use crate::sender::{CommsSender, SendError};
-use crate::types::{CommsChannel, QueuedComms};
+use crate::{CommsChannel, QueuedComms};
 
 pub struct EmailSender {
     from: Mailbox,
@@ -193,9 +193,22 @@ impl CommsSender for EmailSender {
         CommsChannel::Email
     }
 
-    async fn send(&self, notification: &QueuedComms) -> Result<(), SendError> {
-        let mut message =
-            message::build(&self.from, notification, wants_atmos_categories(&self.mode))?;
+    async fn send(
+        &self,
+        notification: &QueuedComms,
+        recipient: &tranquil_types::Recipient,
+    ) -> Result<(), SendError> {
+        let tranquil_types::Recipient::Email(address) = recipient else {
+            return Err(SendError::InvalidRecipient(
+                "Recipient isn't an email address".into(),
+            ));
+        };
+        let mut message = message::build(
+            &self.from,
+            notification,
+            address,
+            wants_atmos_categories(&self.mode),
+        )?;
         if let Some(signer) = &self.dkim {
             signer.sign(&mut message);
         }

crates/tranquil-comms/src/lib.rs

@@ -1,7 +1,6 @@
 pub mod email;
 mod locale;
 mod sender;
-mod types;
 
 pub use email::EmailSender;
 pub use locale::{
@@ -10,6 +9,5 @@ pub use locale::{
 };
 pub use sender::{
     CommsSender, DiscordSender, SendError, SignalSender, TelegramSender, is_valid_phone_number,
-    is_valid_signal_username,
 };
-pub use types::{CommsChannel, CommsStatus, CommsType, NewComms, QueuedComms};
+pub use tranquil_db_traits::{CommsChannel, CommsStatus, CommsType, QueuedComms};

crates/tranquil-comms/src/sender.rs

@@ -3,7 +3,7 @@ use reqwest::Client;
 use serde_json::json;
 use std::time::Duration;
 
-use super::types::{CommsChannel, QueuedComms};
+use tranquil_db_traits::{CommsChannel, QueuedComms};
 
 const HTTP_TIMEOUT_SECS: u64 = 30;
 const MAX_RETRIES: u32 = 3;
@@ -12,7 +12,11 @@ const INITIAL_RETRY_DELAY_MS: u64 = 500;
 #[async_trait]
 pub trait CommsSender: Send + Sync {
     fn channel(&self) -> CommsChannel;
-    async fn send(&self, notification: &QueuedComms) -> Result<(), SendError>;
+    async fn send(
+        &self,
+        notification: &QueuedComms,
+        recipient: &tranquil_types::Recipient,
+    ) -> Result<(), SendError>;
 }
 
 #[derive(Debug, thiserror::Error)]
@@ -140,10 +144,6 @@ pub fn is_valid_phone_number(number: &str) -> bool {
     !remaining.is_empty() && remaining.chars().all(|c| c.is_ascii_digit())
 }
 
-pub fn is_valid_signal_username(username: &str) -> bool {
-    tranquil_signal::SignalUsername::parse(username).is_ok()
-}
-
 const DISCORD_API_BASE: &str = "https://discord.com/api/v10";
 
 #[derive(Clone)]
@@ -355,8 +355,17 @@ impl CommsSender for DiscordSender {
         CommsChannel::Discord
     }
 
-    async fn send(&self, notification: &QueuedComms) -> Result<(), SendError> {
-        let channel_id = self.open_dm_channel(&notification.recipient).await?;
+    async fn send(
+        &self,
+        notification: &QueuedComms,
+        recipient: &tranquil_types::Recipient,
+    ) -> Result<(), SendError> {
+        let tranquil_types::Recipient::Discord(user_id) = recipient else {
+            return Err(SendError::InvalidRecipient(
+                "Recipient isn't a Discord user ID".into(),
+            ));
+        };
+        let channel_id = self.open_dm_channel(user_id.as_str()).await?;
 
         let subject = notification.subject.as_deref().unwrap_or("Notification");
         let content = format!("**{}**\n\n{}", subject, notification.body);
@@ -453,14 +462,22 @@ impl CommsSender for TelegramSender {
         CommsChannel::Telegram
     }
 
-    async fn send(&self, notification: &QueuedComms) -> Result<(), SendError> {
-        let chat_id = &notification.recipient;
+    async fn send(
+        &self,
+        notification: &QueuedComms,
+        recipient: &tranquil_types::Recipient,
+    ) -> Result<(), SendError> {
+        let tranquil_types::Recipient::Telegram(chat_id) = recipient else {
+            return Err(SendError::InvalidRecipient(
+                "Recipient isn't a Telegram chat ID".into(),
+            ));
+        };
         let subject = escape_html(notification.subject.as_deref().unwrap_or("Notification"));
         let body = escape_html(&notification.body);
         let text = format!("<b>{}</b>\n\n{}", subject, body);
         let url = format!("https://api.telegram.org/bot{}/sendMessage", self.bot_token);
         let payload = json!({
-            "chat_id": chat_id,
+            "chat_id": chat_id.as_str(),
             "text": text,
             "parse_mode": "HTML"
         });
@@ -488,9 +505,16 @@ impl CommsSender for SignalSender {
         CommsChannel::Signal
     }
 
-    async fn send(&self, notification: &QueuedComms) -> Result<(), SendError> {
-        let username = tranquil_signal::SignalUsername::parse(&notification.recipient)
-            .map_err(|e| SendError::InvalidRecipient(e.to_string()))?;
+    async fn send(
+        &self,
+        notification: &QueuedComms,
+        recipient: &tranquil_types::Recipient,
+    ) -> Result<(), SendError> {
+        let tranquil_types::Recipient::Signal(username) = recipient else {
+            return Err(SendError::InvalidRecipient(
+                "Recipient isn't a Signal username".into(),
+            ));
+        };
 
         let client = self
             .slot
@@ -505,7 +529,7 @@ impl CommsSender for SignalSender {
 
         let mut last_error = None;
         for attempt in 0..MAX_RETRIES {
-            match client.send(&username, message.clone()).await {
+            match client.send(username, message.clone()).await {
                 Ok(()) => return Ok(()),
                 Err(e) => {
                     let err_str = e.to_string();

crates/tranquil-comms/src/types.rs

@@ -1,51 +0,0 @@
-use uuid::Uuid;
-
-pub use tranquil_db_traits::{CommsChannel, CommsStatus, CommsType, QueuedComms};
-
-pub struct NewComms {
-    pub user_id: Uuid,
-    pub channel: CommsChannel,
-    pub comms_type: CommsType,
-    pub recipient: String,
-    pub subject: Option<String>,
-    pub body: String,
-    pub metadata: Option<serde_json::Value>,
-}
-
-impl NewComms {
-    pub fn new(
-        user_id: Uuid,
-        channel: CommsChannel,
-        comms_type: CommsType,
-        recipient: String,
-        subject: Option<String>,
-        body: String,
-    ) -> Self {
-        Self {
-            user_id,
-            channel,
-            comms_type,
-            recipient,
-            subject,
-            body,
-            metadata: None,
-        }
-    }
-
-    pub fn email(
-        user_id: Uuid,
-        comms_type: CommsType,
-        recipient: String,
-        subject: String,
-        body: String,
-    ) -> Self {
-        Self::new(
-            user_id,
-            CommsChannel::Email,
-            comms_type,
-            recipient,
-            Some(subject),
-            body,
-        )
-    }
-}

crates/tranquil-comms/tests/email_smtp.rs

@@ -32,6 +32,10 @@ fn fixture(recipient: &str, subject: &str, body: &str) -> QueuedComms {
     }
 }
 
+fn to(recipient: &str) -> tranquil_types::Recipient {
+    tranquil_types::Recipient::new(CommsChannel::Email, recipient).unwrap()
+}
+
 fn build_smarthost_sender(host: &str, port: u16) -> EmailSender {
     build_smarthost_sender_with_total_timeout(host, port, Duration::from_secs(10))
 }
@@ -101,7 +105,9 @@ async fn spawn_stub(rcpt_response: &'static [u8]) -> u16 {
 async fn rcpt_550_classifies_as_smtp_permanent() {
     let port = spawn_stub(b"550 5.1.1 user unknown\r\n").await;
     let sender = build_smarthost_sender("127.0.0.1", port);
-    let result = sender.send(&fixture("nel@nel.pet", "x", "x")).await;
+    let result = sender
+        .send(&fixture("oys@nel.pet", "x", "x"), &to("oys@nel.pet"))
+        .await;
     match result {
         Err(SendError::SmtpPermanent(_)) => {}
         other => panic!("expected SmtpPermanent, got {other:?}"),
@@ -112,7 +118,9 @@ async fn rcpt_550_classifies_as_smtp_permanent() {
 async fn rcpt_421_classifies_as_smtp_transient() {
     let port = spawn_stub(b"421 4.7.0 try again later\r\n").await;
     let sender = build_smarthost_sender("127.0.0.1", port);
-    let result = sender.send(&fixture("nel@nel.pet", "x", "x")).await;
+    let result = sender
+        .send(&fixture("oys@nel.pet", "x", "x"), &to("oys@nel.pet"))
+        .await;
     match result {
         Err(SendError::SmtpTransient(_)) => {}
         other => panic!("expected SmtpTransient, got {other:?}"),
@@ -120,10 +128,13 @@ async fn rcpt_421_classifies_as_smtp_transient() {
 }
 
 #[tokio::test]
-async fn invalid_recipient_classifies_as_invalid_recipient() {
+async fn send_rejects_mismatched_recipient_variant() {
     let port = spawn_stub(b"250 OK\r\n").await;
     let sender = build_smarthost_sender("127.0.0.1", port);
-    let result = sender.send(&fixture("not-an-address", "x", "x")).await;
+    let recipient = tranquil_types::Recipient::new(CommsChannel::Signal, "oys.01").unwrap();
+    let result = sender
+        .send(&fixture("oys@nel.pet", "x", "x"), &recipient)
+        .await;
     match result {
         Err(SendError::InvalidRecipient(_)) => {}
         other => panic!("expected InvalidRecipient, got {other:?}"),
@@ -146,7 +157,9 @@ async fn smarthost_silent_relay_hits_total_timeout() {
     let sender =
         build_smarthost_sender_with_total_timeout("127.0.0.1", port, Duration::from_millis(500));
     let start = std::time::Instant::now();
-    let result = sender.send(&fixture("nel@nel.pet", "x", "x")).await;
+    let result = sender
+        .send(&fixture("oys@nel.pet", "x", "x"), &to("oys@nel.pet"))
+        .await;
     let elapsed = start.elapsed();
     match result {
         Err(SendError::Timeout) => {}

crates/tranquil-db-traits/src/infra.rs

@@ -44,60 +44,7 @@ impl InviteCodeState {
     }
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize, sqlx::Type)]
-#[serde(rename_all = "lowercase")]
-#[sqlx(type_name = "comms_channel", rename_all = "snake_case")]
-pub enum CommsChannel {
-    Email,
-    Discord,
-    Telegram,
-    Signal,
-}
-
-impl CommsChannel {
-    pub fn as_str(self) -> &'static str {
-        match self {
-            Self::Email => "email",
-            Self::Discord => "discord",
-            Self::Telegram => "telegram",
-            Self::Signal => "signal",
-        }
-    }
-
-    pub fn display_name(self) -> &'static str {
-        match self {
-            Self::Email => "email",
-            Self::Discord => "Discord",
-            Self::Telegram => "Telegram",
-            Self::Signal => "Signal",
-        }
-    }
-}
-
-impl std::str::FromStr for CommsChannel {
-    type Err = InvalidCommsChannel;
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        match s {
-            "email" => Ok(Self::Email),
-            "discord" => Ok(Self::Discord),
-            "telegram" => Ok(Self::Telegram),
-            "signal" => Ok(Self::Signal),
-            _ => Err(InvalidCommsChannel),
-        }
-    }
-}
-
-#[derive(Debug, Clone)]
-pub struct InvalidCommsChannel;
-
-impl std::fmt::Display for InvalidCommsChannel {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        f.write_str("invalid comms channel")
-    }
-}
-
-impl std::error::Error for InvalidCommsChannel {}
+pub use tranquil_types::{CommsChannel, Recipient};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, sqlx::Type)]
 #[sqlx(type_name = "comms_type", rename_all = "snake_case")]
@@ -226,9 +173,8 @@ pub trait InfraRepository: Send + Sync {
     async fn enqueue_comms(
         &self,
         user_id: Option<Uuid>,
-        channel: CommsChannel,
+        recipient: &Recipient,
         comms_type: CommsType,
-        recipient: &str,
         subject: Option<&str>,
         body: &str,
         metadata: Option<serde_json::Value>,

crates/tranquil-db-traits/src/lib.rs

@@ -25,7 +25,7 @@ pub use infra::{
     AdminAccountInfo, CommsChannel, CommsStatus, CommsType, DeletionRequest,
     DeletionRequestWithToken, InfraRepository, InviteCodeInfo, InviteCodeRow, InviteCodeSortOrder,
     InviteCodeState, InviteCodeUse, NotificationHistoryRow, PasswordResetInfo, PlcTokenInfo,
-    QueuedComms, ReservedSigningKey, ReservedSigningKeyFull,
+    QueuedComms, Recipient, ReservedSigningKey, ReservedSigningKeyFull,
 };
 pub use invite_code::{InviteCodeError, ValidatedInviteCode};
 pub use oauth::{

crates/tranquil-db-traits/src/user.rs

@@ -220,7 +220,11 @@ pub trait UserRepository: Send + Sync {
         channel: CommsChannel,
     ) -> Result<Option<bool>, DbError>;
 
-    async fn admin_update_email(&self, did: &Did, email: &str) -> Result<u64, DbError>;
+    async fn admin_update_email(
+        &self,
+        did: &Did,
+        email: &tranquil_types::EmailAddress,
+    ) -> Result<u64, DbError>;
 
     async fn admin_update_handle(&self, did: &Did, handle: &Handle) -> Result<u64, DbError>;
 
@@ -266,13 +270,11 @@ pub trait UserRepository: Send + Sync {
 
     async fn store_telegram_chat_id(
         &self,
-        telegram_username: &str,
+        telegram_username: &tranquil_types::TelegramUsername,
         chat_id: i64,
         handle: Option<&Handle>,
     ) -> Result<Option<Uuid>, DbError>;
 
-    async fn get_telegram_chat_id(&self, user_id: Uuid) -> Result<Option<i64>, DbError>;
-
     async fn set_unverified_discord(
         &self,
         user_id: Uuid,
@@ -281,8 +283,8 @@ pub trait UserRepository: Send + Sync {
 
     async fn store_discord_user_id(
         &self,
-        discord_username: &str,
-        discord_id: &str,
+        discord_username: &tranquil_types::DiscordUsername,
+        discord_id: &tranquil_types::DiscordUserId,
         handle: Option<&Handle>,
     ) -> Result<Option<Uuid>, DbError>;
 
@@ -911,6 +913,25 @@ pub struct UserResendVerification {
     pub channel_verification: ChannelVerificationStatus,
 }
 
+macro_rules! channel_identifier {
+    ($name:ty) => {
+        impl $name {
+            pub fn channel_identifier(&self) -> Option<&str> {
+                match self.channel {
+                    CommsChannel::Email => self.email.as_deref(),
+                    CommsChannel::Discord => self.discord_username.as_deref(),
+                    CommsChannel::Telegram => self.telegram_username.as_deref(),
+                    CommsChannel::Signal => self.signal_username.as_deref(),
+                }
+                .filter(|identifier| !identifier.is_empty())
+            }
+        }
+    };
+}
+
+channel_identifier!(UserConfirmSignup);
+channel_identifier!(UserResendVerification);
+
 #[derive(Debug, Clone)]
 pub struct UserResetCodeInfo {
     pub id: Uuid,

crates/tranquil-db/src/postgres/infra.rs

@@ -5,7 +5,7 @@ use tranquil_db_traits::{
     AdminAccountInfo, CommsChannel, CommsStatus, CommsType, DbError, DeletionRequest,
     DeletionRequestWithToken, InfraRepository, InviteCodeError, InviteCodeInfo, InviteCodeRow,
     InviteCodeSortOrder, InviteCodeState, InviteCodeUse, NotificationHistoryRow, PlcTokenInfo,
-    QueuedComms, ReservedSigningKey, ReservedSigningKeyFull, ValidatedInviteCode,
+    QueuedComms, Recipient, ReservedSigningKey, ReservedSigningKeyFull, ValidatedInviteCode,
 };
 use tranquil_types::{Did, InviteCode};
 use uuid::Uuid;
@@ -29,9 +29,8 @@ impl InfraRepository for PostgresInfraRepository {
     async fn enqueue_comms(
         &self,
         user_id: Option<Uuid>,
-        channel: CommsChannel,
+        recipient: &Recipient,
         comms_type: CommsType,
-        recipient: &str,
         subject: Option<&str>,
         body: &str,
         metadata: Option<serde_json::Value>,
@@ -42,9 +41,9 @@ impl InfraRepository for PostgresInfraRepository {
                VALUES ($1, $2, $3, $4, $5, $6, $7)
                RETURNING id"#,
             user_id,
-            channel as CommsChannel,
+            recipient.channel() as CommsChannel,
             comms_type as CommsType,
-            recipient,
+            recipient.as_str(),
             subject,
             body,
             metadata

crates/tranquil-db/src/postgres/user.rs

@@ -660,10 +660,14 @@ impl UserRepository for PostgresUserRepository {
         }))
     }
 
-    async fn admin_update_email(&self, did: &Did, email: &str) -> Result<u64, DbError> {
+    async fn admin_update_email(
+        &self,
+        did: &Did,
+        email: &tranquil_types::EmailAddress,
+    ) -> Result<u64, DbError> {
         let result = sqlx::query!(
             "UPDATE users SET email = $1 WHERE did = $2",
-            email,
+            email.as_str(),
             did.as_str()
         )
         .execute(&self.pool)
@@ -3300,10 +3304,11 @@ impl UserRepository for PostgresUserRepository {
 
     async fn store_discord_user_id(
         &self,
-        discord_username: &str,
-        discord_id: &str,
+        discord_username: &tranquil_types::DiscordUsername,
+        discord_id: &tranquil_types::DiscordUserId,
         handle: Option<&Handle>,
     ) -> Result<Option<Uuid>, DbError> {
+        let (discord_username, discord_id) = (discord_username.as_str(), discord_id.as_str());
         let result = match handle {
             Some(h) => sqlx::query_scalar!(
                 "UPDATE users SET discord_id = $2, discord_verified = TRUE, updated_at = NOW() WHERE LOWER(discord_username) = LOWER($1) AND discord_username IS NOT NULL AND handle = $3 RETURNING id",
@@ -3362,10 +3367,11 @@ impl UserRepository for PostgresUserRepository {
 
     async fn store_telegram_chat_id(
         &self,
-        telegram_username: &str,
+        telegram_username: &tranquil_types::TelegramUsername,
         chat_id: i64,
         handle: Option<&Handle>,
     ) -> Result<Option<Uuid>, DbError> {
+        let telegram_username = telegram_username.as_str();
         let result = match handle {
             Some(h) => sqlx::query_scalar!(
                 "UPDATE users SET telegram_chat_id = $2, telegram_verified = TRUE, updated_at = NOW() WHERE LOWER(telegram_username) = LOWER($1) AND telegram_username IS NOT NULL AND handle = $3 RETURNING id",
@@ -3393,14 +3399,6 @@ impl UserRepository for PostgresUserRepository {
         Ok(result)
     }
 
-    async fn get_telegram_chat_id(&self, user_id: Uuid) -> Result<Option<i64>, DbError> {
-        let row = sqlx::query_scalar!("SELECT telegram_chat_id FROM users WHERE id = $1", user_id)
-            .fetch_optional(&self.pool)
-            .await
-            .map_err(map_sqlx_error)?;
-        Ok(row.flatten())
-    }
-
     async fn get_password_reset_info(
         &self,
         email: &str,

crates/tranquil-oauth-server/src/endpoints/authorize/login.rs

@@ -572,20 +572,31 @@ pub async fn authorize_post(
         {
             Ok(challenge) => {
                 let hostname = &tranquil_config::get().server.hostname;
-                if let Err(e) = enqueue_2fa_code(
+                match enqueue_notice(
                     state.repos.user.as_ref(),
                     state.repos.infra.as_ref(),
                     user.id,
-                    &challenge.code,
+                    Notice::TwoFactorCode {
+                        code: &challenge.code,
+                    },
                     hostname,
                 )
                 .await
                 {
-                    tracing::warn!(
-                        did = %user.did,
-                        error = %e,
-                        "Failed to enqueue 2FA notification"
-                    );
+                    Ok(Some(_)) => {}
+                    Ok(None) => {
+                        return show_login_error(
+                            "We couldn't deliver this verification code to your notification channels. Please contact the PDS owner.",
+                            json_response,
+                        );
+                    }
+                    Err(e) => {
+                        tracing::warn!(
+                            did = %user.did,
+                            error = %e,
+                            "Failed to enqueue 2FA notification"
+                        );
+                    }
                 }
                 let channel_name = user.preferred_comms_channel.display_name();
                 if json_response {
@@ -907,20 +918,32 @@ pub async fn authorize_select(
         {
             Ok(challenge) => {
                 let hostname = &tranquil_config::get().server.hostname;
-                if let Err(e) = enqueue_2fa_code(
+                match enqueue_notice(
                     state.repos.user.as_ref(),
                     state.repos.infra.as_ref(),
                     user.id,
-                    &challenge.code,
+                    Notice::TwoFactorCode {
+                        code: &challenge.code,
+                    },
                     hostname,
                 )
                 .await
                 {
-                    tracing::warn!(
-                        did = %form.did,
-                        error = %e,
-                        "Failed to enqueue 2FA notification"
-                    );
+                    Ok(Some(_)) => {}
+                    Ok(None) => {
+                        return json_error(
+                            StatusCode::BAD_REQUEST,
+                            "invalid_request",
+                            "We couldn't deliver this verification code to your notification chanels. Please contact the PDS owner.",
+                        );
+                    }
+                    Err(e) => {
+                        tracing::warn!(
+                            did = %form.did,
+                            error = %e,
+                            "Failed to enqueue 2FA notification"
+                        );
+                    }
                 }
                 let channel_name = user.preferred_comms_channel.display_name();
                 return Json(serde_json::json!({

crates/tranquil-oauth-server/src/endpoints/authorize/mod.rs

@@ -12,7 +12,8 @@ use serde::{Deserialize, Serialize};
 use subtle::ConstantTimeEq;
 use tranquil_db_traits::{ScopePreference, WebauthnChallengeType};
 use tranquil_pds::auth::{BareLoginIdentifier, NormalizedLoginIdentifier};
-use tranquil_pds::comms::comms_repo::enqueue_2fa_code;
+use tranquil_pds::comms::Notice;
+use tranquil_pds::comms::comms_repo::enqueue_notice;
 use tranquil_pds::oauth::{
     AuthFlow, DeviceData, DeviceId, OAuthError, Prompt, SessionId, db::should_show_consent,
 };

crates/tranquil-oauth-server/src/endpoints/authorize/passkey.rs

@@ -1273,16 +1273,31 @@ pub async fn authorize_passkey_finish(
                 .await
             {
                 Ok(challenge) => {
-                    if let Err(e) = enqueue_2fa_code(
+                    match enqueue_notice(
                         state.repos.user.as_ref(),
                         state.repos.infra.as_ref(),
                         user.id,
-                        &challenge.code,
+                        Notice::TwoFactorCode {
+                            code: &challenge.code,
+                        },
                         pds_hostname,
                     )
                     .await
                     {
-                        tracing::warn!(did = %did, error = %e, "Failed to enqueue 2FA notification");
+                        Ok(Some(_)) => {}
+                        Ok(None) => {
+                            return (
+                                StatusCode::BAD_REQUEST,
+                                Json(serde_json::json!({
+                                    "error": "invalid_request",
+                                    "error_description": "We couldn't deliver the verification code to your notification channels. Please contact the PDS owner! <3"
+                                })),
+                            )
+                                .into_response();
+                        }
+                        Err(e) => {
+                            tracing::warn!(did = %did, error = %e, "Failed to enqueue 2FA notification");
+                        }
                     }
                     let channel_name = user.preferred_comms_channel.display_name();
                     let redirect_url = format!(

crates/tranquil-oauth-server/src/sso_endpoints.rs

@@ -916,55 +916,26 @@ pub async fn complete_registration(
     let verification_channel = input
         .verification_channel
         .unwrap_or(tranquil_db_traits::CommsChannel::Email);
-    let verification_recipient = match verification_channel {
-        tranquil_db_traits::CommsChannel::Email => {
-            let email = input
-                .email
+    let effective_email = input
+        .email
+        .clone()
+        .or_else(|| {
+            pending_preview
+                .provider_email
                 .clone()
-                .or_else(|| {
-                    pending_preview
-                        .provider_email
-                        .clone()
-                        .map(|e| e.into_inner())
-                })
-                .map(|e| e.trim().to_string())
-                .filter(|e| !e.is_empty());
-            match email {
-                Some(e) if !e.is_empty() => e,
-                _ => return Err(ApiError::MissingEmail),
-            }
-        }
-        tranquil_db_traits::CommsChannel::Discord => match &input.discord_username {
-            Some(username) if !username.trim().is_empty() => {
-                let clean = username.trim().to_lowercase();
-                if !tranquil_pds::api::validation::is_valid_discord_username(&clean) {
-                    return Err(ApiError::InvalidRequest(
-                        "Invalid Discord username. Must be 2-32 lowercase characters (letters, numbers, underscores, periods)".into(),
-                    ));
-                }
-                clean
-            }
-            _ => return Err(ApiError::MissingDiscordId),
+                .map(|e| e.into_inner())
+        })
+        .map(|e| e.trim().to_string())
+        .filter(|e| !e.is_empty());
+    let target = tranquil_api::common::extract_verification_recipient(
+        verification_channel,
+        &tranquil_api::common::ChannelInput {
+            email: effective_email.as_deref(),
+            discord_username: input.discord_username.as_deref(),
+            telegram_username: input.telegram_username.as_deref(),
+            signal_username: input.signal_username.as_deref(),
         },
-        tranquil_db_traits::CommsChannel::Telegram => match &input.telegram_username {
-            Some(username) if !username.trim().is_empty() => {
-                let clean = username.trim().trim_start_matches('@');
-                if !tranquil_pds::api::validation::is_valid_telegram_username(clean) {
-                    return Err(ApiError::InvalidRequest(
-                        "Invalid Telegram username. Must be 5-32 characters, alphanumeric or underscore".into(),
-                    ));
-                }
-                clean.to_string()
-            }
-            _ => return Err(ApiError::MissingTelegramUsername),
-        },
-        tranquil_db_traits::CommsChannel::Signal => match &input.signal_username {
-            Some(username) if !username.trim().is_empty() => {
-                username.trim().trim_start_matches('@').to_lowercase()
-            }
-            _ => return Err(ApiError::MissingSignalNumber),
-        },
-    };
+    )?;
 
     let email = input
         .email
@@ -978,18 +949,11 @@ pub async fn complete_registration(
         .map(|e| e.trim().to_string())
         .filter(|e| !e.is_empty());
 
-    let email = match &email {
-        Some(e) => {
-            if e.len() > 254 {
-                return Err(ApiError::InvalidEmail);
-            }
-            if !tranquil_pds::api::validation::is_valid_email(e) {
-                return Err(ApiError::InvalidEmail);
-            }
-            Some(e.clone())
-        }
-        None => None,
-    };
+    if let Some(e) = &email
+        && tranquil_types::EmailAddress::new(e).is_err()
+    {
+        return Err(ApiError::InvalidEmail);
+    }
 
     let invite_registration =
         check_registration_invite(&state, input.invite_code.as_deref()).await?;
@@ -1336,10 +1300,11 @@ pub async fn complete_registration(
             }
 
             let hostname = &tranquil_config::get().server.hostname;
-            if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_welcome(
+            if let Err(e) = tranquil_pds::comms::comms_repo::enqueue_notice(
                 state.repos.user.as_ref(),
                 state.repos.infra.as_ref(),
                 user_id.unwrap_or(uuid::Uuid::nil()),
+                tranquil_pds::comms::Notice::Welcome,
                 hostname,
             )
             .await
@@ -1376,7 +1341,7 @@ pub async fn complete_registration(
         let verification_token = tranquil_pds::auth::verification_token::generate_signup_token(
             &did,
             verification_channel,
-            &verification_recipient,
+            &target.id,
         );
         let formatted_token =
             tranquil_pds::auth::verification_token::format_token_for_display(&verification_token);
@@ -1384,8 +1349,7 @@ pub async fn complete_registration(
             state.repos.user.as_ref(),
             state.repos.infra.as_ref(),
             uid,
-            verification_channel,
-            &verification_recipient,
+            &target,
             &formatted_token,
             hostname,
         )

crates/tranquil-pds/src/api/error.rs

@@ -775,6 +775,31 @@ impl From<jacquard_common::types::string::AtStrError> for ApiError {
     }
 }
 
+impl From<tranquil_types::InvalidEmailAddress> for ApiError {
+    fn from(_: tranquil_types::InvalidEmailAddress) -> Self {
+        Self::InvalidEmail
+    }
+}
+
+macro_rules! invalid_request_from {
+    ($($err:ty),* $(,)?) => {
+        $(
+            impl From<$err> for ApiError {
+                fn from(e: $err) -> Self {
+                    Self::InvalidRequest(e.to_string())
+                }
+            }
+        )*
+    };
+}
+
+invalid_request_from!(
+    tranquil_types::InvalidSignalUsername,
+    tranquil_types::InvalidTelegramUsername,
+    tranquil_types::InvalidDiscordUsername,
+    tranquil_types::InvalidRecipient,
+);
+
 impl From<crate::plc::PlcError> for ApiError {
     fn from(e: crate::plc::PlcError) -> Self {
         use crate::plc::PlcError;

crates/tranquil-pds/src/api/validation.rs

@@ -1,102 +1,11 @@
 use crate::types::Handle;
-use std::fmt;
 
-pub const MAX_EMAIL_LENGTH: usize = 254;
-pub const MAX_LOCAL_PART_LENGTH: usize = 64;
-pub const MAX_DOMAIN_LENGTH: usize = 253;
 pub const MAX_DOMAIN_LABEL_LENGTH: usize = 63;
-const EMAIL_LOCAL_SPECIAL_CHARS: &str = ".!#$%&'*+/=?^_`{|}~-";
 
 pub const MIN_HANDLE_LENGTH: usize = 3;
 pub const MAX_HANDLE_LENGTH: usize = 253;
 pub const MAX_SERVICE_HANDLE_LOCAL_PART: usize = 18;
 
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum EmailValidationError {
-    Empty,
-    TooLong,
-    MissingAtSign,
-    EmptyLocalPart,
-    LocalPartTooLong,
-    InvalidLocalPart,
-    EmptyDomain,
-    DomainTooLong,
-    MissingDomainDot,
-    InvalidDomainLabel,
-}
-
-impl fmt::Display for EmailValidationError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Self::Empty => write!(f, "Email cannot be empty"),
-            Self::TooLong => write!(
-                f,
-                "Email exceeds maximum length of {} characters",
-                MAX_EMAIL_LENGTH
-            ),
-            Self::MissingAtSign => write!(f, "Email must contain @"),
-            Self::EmptyLocalPart => write!(f, "Email local part cannot be empty"),
-            Self::LocalPartTooLong => write!(f, "Email local part exceeds maximum length"),
-            Self::InvalidLocalPart => write!(f, "Email local part contains invalid characters"),
-            Self::EmptyDomain => write!(f, "Email domain cannot be empty"),
-            Self::DomainTooLong => write!(f, "Email domain exceeds maximum length"),
-            Self::MissingDomainDot => write!(f, "Email domain must contain a dot"),
-            Self::InvalidDomainLabel => write!(f, "Email domain contains invalid label"),
-        }
-    }
-}
-
-impl std::error::Error for EmailValidationError {}
-
-fn validate_email_detailed(email: &str) -> Result<(), EmailValidationError> {
-    if email.is_empty() {
-        return Err(EmailValidationError::Empty);
-    }
-    if email.len() > MAX_EMAIL_LENGTH {
-        return Err(EmailValidationError::TooLong);
-    }
-    let parts: Vec<&str> = email.rsplitn(2, '@').collect();
-    if parts.len() != 2 {
-        return Err(EmailValidationError::MissingAtSign);
-    }
-    let domain = parts[0];
-    let local = parts[1];
-    if local.is_empty() {
-        return Err(EmailValidationError::EmptyLocalPart);
-    }
-    if local.len() > MAX_LOCAL_PART_LENGTH {
-        return Err(EmailValidationError::LocalPartTooLong);
-    }
-    if local.starts_with('.') || local.ends_with('.') || local.contains("..") {
-        return Err(EmailValidationError::InvalidLocalPart);
-    }
-    if !local
-        .chars()
-        .all(|c| c.is_ascii_alphanumeric() || EMAIL_LOCAL_SPECIAL_CHARS.contains(c))
-    {
-        return Err(EmailValidationError::InvalidLocalPart);
-    }
-    if domain.is_empty() {
-        return Err(EmailValidationError::EmptyDomain);
-    }
-    if domain.len() > MAX_DOMAIN_LENGTH {
-        return Err(EmailValidationError::DomainTooLong);
-    }
-    if !domain.contains('.') {
-        return Err(EmailValidationError::MissingDomainDot);
-    }
-    if !domain.split('.').all(|label| {
-        !label.is_empty()
-            && label.len() <= MAX_DOMAIN_LABEL_LENGTH
-            && !label.starts_with('-')
-            && !label.ends_with('-')
-            && label.chars().all(|c| c.is_ascii_alphanumeric() || c == '-')
-    }) {
-        return Err(EmailValidationError::InvalidDomainLabel);
-    }
-    Ok(())
-}
-
 #[derive(Debug, PartialEq)]
 pub enum HandleValidationError {
     Empty,
@@ -304,23 +213,6 @@ pub fn validate_service_handle(
     Ok(handle.to_lowercase())
 }
 
-pub fn is_valid_email(email: &str) -> bool {
-    validate_email_detailed(email.trim()).is_ok()
-}
-
-pub fn is_valid_telegram_username(username: &str) -> bool {
-    let clean = username.strip_prefix('@').unwrap_or(username);
-    (5..=32).contains(&clean.len()) && clean.chars().all(|c| c.is_ascii_alphanumeric() || c == '_')
-}
-
-pub fn is_valid_discord_username(username: &str) -> bool {
-    (2..=32).contains(&username.len())
-        && username
-            .chars()
-            .all(|c| c.is_ascii_lowercase() || c.is_ascii_digit() || c == '_' || c == '.')
-        && !username.contains("..")
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -487,62 +379,4 @@ mod tests {
             Err(HandleValidationError::Reserved)
         );
     }
-
-    #[test]
-    fn test_valid_emails() {
-        assert!(is_valid_email("user@example.com"));
-        assert!(is_valid_email("user.name@example.com"));
-        assert!(is_valid_email("user+tag@example.com"));
-        assert!(is_valid_email("user@sub.example.com"));
-        assert!(is_valid_email("USER@EXAMPLE.COM"));
-        assert!(is_valid_email("user123@example123.com"));
-        assert!(is_valid_email("a@b.co"));
-    }
-    #[test]
-    fn test_invalid_emails() {
-        assert!(!is_valid_email(""));
-        assert!(!is_valid_email("user"));
-        assert!(!is_valid_email("user@"));
-        assert!(!is_valid_email("@example.com"));
-        assert!(!is_valid_email("user@example"));
-        assert!(!is_valid_email("user@@example.com"));
-        assert!(!is_valid_email("user@.example.com"));
-        assert!(!is_valid_email("user@example..com"));
-        assert!(!is_valid_email(".user@example.com"));
-        assert!(!is_valid_email("user.@example.com"));
-        assert!(!is_valid_email("user..name@example.com"));
-        assert!(!is_valid_email("user@-example.com"));
-        assert!(!is_valid_email("user@example-.com"));
-    }
-    #[test]
-    fn test_trimmed_whitespace() {
-        assert!(is_valid_email("  user@example.com  "));
-    }
-
-    #[test]
-    fn test_valid_discord_usernames() {
-        assert!(is_valid_discord_username("ab"));
-        assert!(is_valid_discord_username("alice"));
-        assert!(is_valid_discord_username("user_name"));
-        assert!(is_valid_discord_username("user.name"));
-        assert!(is_valid_discord_username("user123"));
-        assert!(is_valid_discord_username("a_b.c_d"));
-        assert!(is_valid_discord_username(
-            "12345678901234567890123456789012"
-        ));
-    }
-
-    #[test]
-    fn test_invalid_discord_usernames() {
-        assert!(!is_valid_discord_username(""));
-        assert!(!is_valid_discord_username("a"));
-        assert!(!is_valid_discord_username("Alice"));
-        assert!(!is_valid_discord_username("ALICE"));
-        assert!(!is_valid_discord_username("user-name"));
-        assert!(!is_valid_discord_username("user..name"));
-        assert!(!is_valid_discord_username("user name"));
-        assert!(!is_valid_discord_username(
-            "123456789012345678901234567890123"
-        ));
-    }
 }

crates/tranquil-pds/src/comms/mod.rs

@@ -1,10 +1,9 @@
 mod service;
 
+pub use service::repo::Notice;
+pub use service::{CommsService, VerificationTarget, recipient_for, repo as comms_repo};
 pub use tranquil_comms::{
     CommsChannel, CommsSender, CommsStatus, CommsType, DEFAULT_LOCALE, DiscordSender, EmailSender,
-    NewComms, NotificationStrings, QueuedComms, SendError, SignalSender, TelegramSender,
-    VALID_LOCALES, format_message, get_strings, is_valid_phone_number, is_valid_signal_username,
-    validate_locale,
+    NotificationStrings, QueuedComms, SendError, SignalSender, TelegramSender, VALID_LOCALES,
+    format_message, get_strings, is_valid_phone_number, validate_locale,
 };
-
-pub use service::{CommsService, repo as comms_repo, resolve_delivery_channel};

crates/tranquil-pds/src/comms/service.rs

@@ -7,9 +7,13 @@ use chrono::Utc;
 use tokio_util::sync::CancellationToken;
 use tracing::{debug, error, info, warn};
 use tranquil_comms::{
-    CommsChannel, CommsSender, CommsType, NewComms, SendError, format_message, get_strings,
+    CommsChannel, CommsSender, CommsType, NotificationStrings, SendError, format_message,
+    get_strings,
 };
-use tranquil_db_traits::{InfraRepository, QueuedComms, UserCommsPrefs, UserRepository};
+use tranquil_db_traits::{
+    DbError, InfraRepository, QueuedComms, Recipient, UserCommsPrefs, UserRepository,
+};
+use tranquil_types::{DiscordUserId, EmailAddress, SignalUsername, TelegramChatId};
 use uuid::Uuid;
 
 pub struct CommsService {
@@ -47,23 +51,6 @@ impl CommsService {
         self
     }
 
-    pub async fn enqueue(&self, item: NewComms) -> Result<Uuid, tranquil_db_traits::DbError> {
-        let id = self
-            .infra_repo
-            .enqueue_comms(
-                Some(item.user_id),
-                item.channel,
-                item.comms_type,
-                &item.recipient,
-                item.subject.as_deref(),
-                &item.body,
-                item.metadata,
-            )
-            .await?;
-        debug!(comms_id = %id, "Comms enqueued");
-        Ok(id)
-    }
-
     pub fn has_senders(&self) -> bool {
         !self.senders.is_empty()
     }
@@ -126,8 +113,28 @@ impl CommsService {
 
     async fn process_item(&self, item: QueuedComms) {
         let comms_id = item.id;
+
+        // Re-checking because there's been a trip into the DB and back, can't trust type -> string -> *maybe* type
+        let recipient = match tranquil_db_traits::Recipient::new(item.channel, &item.recipient) {
+            Ok(recipient) => recipient,
+            Err(e) => {
+                warn!(
+                    comms_id = %comms_id,
+                    error = %e,
+                    "We marked comms item as permanently failed because its recipient is invalid"
+                );
+                if let Err(db_err) = self.mark_failed_permanent(comms_id, &e.to_string()).await {
+                    error!(
+                        comms_id = %comms_id,
+                        error = %db_err,
+                        "Failed to mark comms as failed"
+                    );
+                }
+                return;
+            }
+        };
         let result = match self.senders.get(&item.channel) {
-            Some(sender) => sender.send(&item).await,
+            Some(sender) => sender.send(&item, &recipient).await,
             None => {
                 warn!(
                     comms_id = %comms_id,
@@ -189,131 +196,234 @@ impl CommsService {
     }
 }
 
-struct ResolvedRecipient {
-    channel: tranquil_db_traits::CommsChannel,
-    recipient: String,
+// Think about the situation on Telegram and Discord where the user must message a given bot *first* in order to hydrate a chat ID into our system so that we can in fact send things.
+// If we can think of a better way to simply error-out later, instead of falling back to email when say Telegram is in an aborted state, let's do that.
+pub struct VerificationTarget {
+    pub id: String,
+    pub recipient: Recipient,
 }
 
-pub fn resolve_delivery_channel(
-    prefs: &UserCommsPrefs,
-    channel: tranquil_db_traits::CommsChannel,
-) -> tranquil_db_traits::CommsChannel {
-    resolve_recipient(prefs, channel).channel
-}
-
-fn resolve_recipient(
-    prefs: &UserCommsPrefs,
-    channel: tranquil_db_traits::CommsChannel,
-) -> ResolvedRecipient {
-    let email_fallback = || ResolvedRecipient {
-        channel: tranquil_db_traits::CommsChannel::Email,
-        recipient: prefs.email.clone().unwrap_or_default(),
-    };
-    match channel {
-        tranquil_db_traits::CommsChannel::Email => email_fallback(),
-        tranquil_db_traits::CommsChannel::Telegram => prefs
-            .telegram_chat_id
-            .map(|id| ResolvedRecipient {
-                channel,
-                recipient: id.to_string(),
-            })
-            .unwrap_or_else(email_fallback),
-        tranquil_db_traits::CommsChannel::Discord => prefs
-            .discord_id
-            .as_ref()
-            .filter(|id| !id.is_empty())
-            .map(|id| ResolvedRecipient {
-                channel,
-                recipient: id.clone(),
-            })
-            .unwrap_or_else(email_fallback),
-        tranquil_db_traits::CommsChannel::Signal => prefs
-            .signal_username
-            .as_ref()
-            .filter(|n| !n.is_empty())
-            .map(|n| ResolvedRecipient {
-                channel,
-                recipient: n.clone(),
-            })
-            .unwrap_or_else(email_fallback),
+impl VerificationTarget {
+    pub fn direct(recipient: Recipient) -> Self {
+        Self {
+            id: recipient.as_str().to_string(),
+            recipient,
+        }
     }
+
+    pub fn resolve(
+        channel: CommsChannel,
+        id: &str,
+        fallback: Option<&str>,
+    ) -> Result<Self, crate::api::error::ApiError> {
+        let direct = (!channel.verifies_via_bot())
+            .then(|| Recipient::new(channel, id))
+            .and_then(Result::ok);
+        let recipient = direct.map_or_else(|| fallback_recipient(fallback), Ok)?;
+        Ok(Self {
+            id: id.to_string(),
+            recipient,
+        })
+    }
+}
+
+fn fallback_recipient(fallback: Option<&str>) -> Result<Recipient, crate::api::error::ApiError> {
+    let raw = fallback
+        .map(str::trim)
+        .filter(|email| !email.is_empty())
+        .ok_or(crate::api::error::ApiError::InvalidRequest(
+            "Verification over this channel needs an email address. Message the bot first".into(),
+        ))?;
+    EmailAddress::new(raw)
+        .map(Recipient::Email)
+        .map_err(|_| crate::api::error::ApiError::InvalidEmail)
+}
+
+pub fn recipient_for(prefs: &UserCommsPrefs, channel: CommsChannel) -> Option<Recipient> {
+    let fallback = || email_recipient(prefs);
+    match channel {
+        CommsChannel::Email => fallback(),
+        CommsChannel::Telegram => prefs
+            .telegram_chat_id
+            .and_then(TelegramChatId::from_i64)
+            .map(Recipient::Telegram)
+            .or_else(fallback),
+        CommsChannel::Discord => prefs
+            .discord_id
+            .as_deref()
+            .and_then(|id| DiscordUserId::new(id).ok())
+            .map(Recipient::Discord)
+            .or_else(fallback),
+        CommsChannel::Signal => prefs
+            .signal_username
+            .as_deref()
+            .and_then(|name| SignalUsername::new(name).ok())
+            .map(Recipient::Signal)
+            .or_else(fallback),
+    }
+}
+
+fn email_recipient(prefs: &UserCommsPrefs) -> Option<Recipient> {
+    prefs
+        .email
+        .as_deref()
+        .and_then(|email| EmailAddress::new(email).ok())
+        .map(Recipient::Email)
 }
 
 pub mod repo {
     use super::*;
-    use tranquil_db_traits::DbError;
 
-    pub async fn enqueue_welcome(
-        user_repo: &dyn UserRepository,
-        infra_repo: &dyn InfraRepository,
-        user_id: Uuid,
-        hostname: &str,
-    ) -> Result<Uuid, DbError> {
-        let prefs = user_repo
-            .get_comms_prefs(user_id)
-            .await?
-            .ok_or(DbError::NotFound)?;
-        let strings = get_strings(prefs.preferred_locale.as_deref().unwrap_or("en"));
-        let body = format_message(
-            strings.welcome_body,
-            &[("hostname", hostname), ("handle", &prefs.handle)],
-        );
-        let subject = format_message(strings.welcome_subject, &[("hostname", hostname)]);
-        let resolved = resolve_recipient(&prefs, prefs.preferred_channel);
-        infra_repo
-            .enqueue_comms(
-                Some(user_id),
-                resolved.channel,
-                CommsType::Welcome,
-                &resolved.recipient,
-                Some(&subject),
-                &body,
-                None,
-            )
-            .await
+    pub enum Notice<'a> {
+        Welcome,
+        PasswordReset { code: &'a str },
+        TwoFactorCode { code: &'a str },
+        AccountDeletion { code: &'a str },
+        PlcOperation { token: &'a str },
+        PasskeyRecovery { url: &'a str },
+        ShortTokenEmail { token: &'a str },
+        LegacyLoginAlert { channel: CommsChannel, ip: &'a str },
     }
 
-    pub async fn enqueue_password_reset(
+    impl Notice<'_> {
+        fn comms_type(&self) -> CommsType {
+            match self {
+                Self::Welcome => CommsType::Welcome,
+                Self::PasswordReset { .. } => CommsType::PasswordReset,
+                Self::TwoFactorCode { .. } => CommsType::TwoFactorCode,
+                Self::AccountDeletion { .. } => CommsType::AccountDeletion,
+                Self::PlcOperation { .. } => CommsType::PlcOperation,
+                Self::PasskeyRecovery { .. } => CommsType::PasskeyRecovery,
+                Self::ShortTokenEmail { .. } => CommsType::EmailUpdate,
+                Self::LegacyLoginAlert { .. } => CommsType::LegacyLoginAlert,
+            }
+        }
+
+        // Yes yes I know, hardcoded, non-email-based accounts will have already bailed by now, don't worry. Emails are not special.
+        fn channel(&self) -> Option<CommsChannel> {
+            match self {
+                Self::ShortTokenEmail { .. } => Some(CommsChannel::Email),
+                Self::LegacyLoginAlert { channel, .. } => Some(*channel),
+                _ => None,
+            }
+        }
+
+        fn subject(&self, strings: &NotificationStrings) -> &'static str {
+            match self {
+                Self::Welcome => strings.welcome_subject,
+                Self::PasswordReset { .. } => strings.password_reset_subject,
+                Self::TwoFactorCode { .. } => strings.two_factor_code_subject,
+                Self::AccountDeletion { .. } => strings.account_deletion_subject,
+                Self::PlcOperation { .. } => strings.plc_operation_subject,
+                Self::PasskeyRecovery { .. } => strings.passkey_recovery_subject,
+                Self::ShortTokenEmail { .. } => strings.email_update_subject,
+                Self::LegacyLoginAlert { .. } => strings.legacy_login_subject,
+            }
+        }
+
+        fn body(&self, strings: &NotificationStrings, handle: &str, hostname: &str) -> String {
+            match self {
+                Self::Welcome => format_message(
+                    strings.welcome_body,
+                    &[("hostname", hostname), ("handle", handle)],
+                ),
+                Self::PasswordReset { code } => format_message(
+                    strings.password_reset_body,
+                    &[("handle", handle), ("code", code)],
+                ),
+                Self::TwoFactorCode { code } => format_message(
+                    strings.two_factor_code_body,
+                    &[("handle", handle), ("code", code)],
+                ),
+                Self::AccountDeletion { code } => format_message(
+                    strings.account_deletion_body,
+                    &[("handle", handle), ("code", code)],
+                ),
+                Self::PlcOperation { token } => format_message(
+                    strings.plc_operation_body,
+                    &[("handle", handle), ("token", token)],
+                ),
+                Self::PasskeyRecovery { url } => format_message(
+                    strings.passkey_recovery_body,
+                    &[("handle", handle), ("url", url)],
+                ),
+                Self::ShortTokenEmail { token } => {
+                    let verify_page = format!("https://{hostname}/app/settings");
+                    format_message(
+                        strings.short_token_body,
+                        &[
+                            ("handle", handle),
+                            ("code", token),
+                            ("verify_page", &verify_page),
+                        ],
+                    )
+                }
+                Self::LegacyLoginAlert { ip, .. } => {
+                    let timestamp = Utc::now().format("%Y-%m-%d %H:%M:%S UTC").to_string();
+                    format_message(
+                        strings.legacy_login_body,
+                        &[
+                            ("handle", handle),
+                            ("timestamp", &timestamp),
+                            ("ip", ip),
+                            ("hostname", hostname),
+                        ],
+                    )
+                }
+            }
+        }
+    }
+
+    pub async fn enqueue_notice(
         user_repo: &dyn UserRepository,
         infra_repo: &dyn InfraRepository,
         user_id: Uuid,
-        code: &str,
+        notice: Notice<'_>,
         hostname: &str,
-    ) -> Result<Uuid, DbError> {
+    ) -> Result<Option<Uuid>, DbError> {
         let prefs = user_repo
             .get_comms_prefs(user_id)
             .await?
             .ok_or(DbError::NotFound)?;
-        let strings = get_strings(prefs.preferred_locale.as_deref().unwrap_or("en"));
-        let body = format_message(
-            strings.password_reset_body,
-            &[("handle", &prefs.handle), ("code", code)],
-        );
-        let subject = format_message(strings.password_reset_subject, &[("hostname", hostname)]);
-        let resolved = resolve_recipient(&prefs, prefs.preferred_channel);
+        let channel = notice.channel().unwrap_or(prefs.preferred_channel);
+        let Some(recipient) = recipient_for(&prefs, channel) else {
+            warn!(
+                user_id = %user_id,
+                channel = ?channel,
+                "We skipped queuing this notice because the account doesn't have a valid recipient"
+            );
+            return Ok(None);
+        };
+        let strings = get_strings(locale_of(&prefs));
+        let subject = format_message(notice.subject(strings), &[("hostname", hostname)]);
+        let body = notice.body(strings, prefs.handle.as_str(), hostname);
         infra_repo
             .enqueue_comms(
                 Some(user_id),
-                resolved.channel,
-                CommsType::PasswordReset,
-                &resolved.recipient,
+                &recipient,
+                notice.comms_type(),
                 Some(&subject),
                 &body,
                 None,
             )
             .await
+            .map(Some)
+    }
+
+    fn locale_of(prefs: &UserCommsPrefs) -> &str {
+        prefs.preferred_locale.as_deref().unwrap_or("en")
     }
 
     pub async fn enqueue_email_update(
         infra_repo: &dyn InfraRepository,
         user_id: Uuid,
-        new_email: &str,
+        new_email: &EmailAddress,
         handle: &crate::types::Handle,
         code: &str,
         hostname: &str,
     ) -> Result<Uuid, DbError> {
         let strings = get_strings("en");
-        let encoded_email = urlencoding::encode(new_email);
+        let encoded_email = urlencoding::encode(new_email.as_str());
         let encoded_token = urlencoding::encode(code);
         let verify_page = format!("https://{}/app/verify", hostname);
         let verify_link = format!(
@@ -333,186 +443,8 @@ pub mod repo {
         infra_repo
             .enqueue_comms(
                 Some(user_id),
-                tranquil_db_traits::CommsChannel::Email,
+                &Recipient::Email(new_email.clone()),
                 CommsType::EmailUpdate,
-                new_email,
-                Some(&subject),
-                &body,
-                None,
-            )
-            .await
-    }
-
-    pub async fn enqueue_email_update_token(
-        user_repo: &dyn UserRepository,
-        infra_repo: &dyn InfraRepository,
-        user_id: Uuid,
-        raw_token: &str,
-        display_code: &str,
-        hostname: &str,
-    ) -> Result<Uuid, DbError> {
-        let prefs = user_repo
-            .get_comms_prefs(user_id)
-            .await?
-            .ok_or(DbError::NotFound)?;
-        let strings = get_strings(prefs.preferred_locale.as_deref().unwrap_or("en"));
-        let current_email = prefs.email.unwrap_or_default();
-        let verify_page = format!("https://{}/app/settings", hostname);
-        let verify_link = format!(
-            "https://{}/xrpc/_account.authorizeEmailUpdate?token={}",
-            hostname,
-            urlencoding::encode(raw_token)
-        );
-        let body = format_message(
-            strings.email_update_body,
-            &[
-                ("handle", &prefs.handle),
-                ("code", display_code),
-                ("verify_page", &verify_page),
-                ("verify_link", &verify_link),
-            ],
-        );
-        let subject = format_message(strings.email_update_subject, &[("hostname", hostname)]);
-        infra_repo
-            .enqueue_comms(
-                Some(user_id),
-                tranquil_db_traits::CommsChannel::Email,
-                CommsType::EmailUpdate,
-                &current_email,
-                Some(&subject),
-                &body,
-                None,
-            )
-            .await
-    }
-
-    pub async fn enqueue_short_token_email(
-        user_repo: &dyn UserRepository,
-        infra_repo: &dyn InfraRepository,
-        user_id: Uuid,
-        token: &str,
-        hostname: &str,
-    ) -> Result<Uuid, DbError> {
-        let prefs = user_repo
-            .get_comms_prefs(user_id)
-            .await?
-            .ok_or(DbError::NotFound)?;
-        let strings = get_strings(prefs.preferred_locale.as_deref().unwrap_or("en"));
-        let current_email = prefs.email.clone().unwrap_or_default();
-
-        let subject_template = strings.email_update_subject;
-        let body_template = strings.short_token_body;
-        let comms_type = CommsType::EmailUpdate;
-
-        let verify_page = format!("https://{}/app/settings", hostname);
-        let body = format_message(
-            body_template,
-            &[
-                ("handle", &prefs.handle),
-                ("code", token),
-                ("verify_page", &verify_page),
-            ],
-        );
-        let subject = format_message(subject_template, &[("hostname", hostname)]);
-        infra_repo
-            .enqueue_comms(
-                Some(user_id),
-                tranquil_db_traits::CommsChannel::Email,
-                comms_type,
-                &current_email,
-                Some(&subject),
-                &body,
-                None,
-            )
-            .await
-    }
-
-    pub async fn enqueue_account_deletion(
-        user_repo: &dyn UserRepository,
-        infra_repo: &dyn InfraRepository,
-        user_id: Uuid,
-        code: &str,
-        hostname: &str,
-    ) -> Result<Uuid, DbError> {
-        let prefs = user_repo
-            .get_comms_prefs(user_id)
-            .await?
-            .ok_or(DbError::NotFound)?;
-        let strings = get_strings(prefs.preferred_locale.as_deref().unwrap_or("en"));
-        let body = format_message(
-            strings.account_deletion_body,
-            &[("handle", &prefs.handle), ("code", code)],
-        );
-        let subject = format_message(strings.account_deletion_subject, &[("hostname", hostname)]);
-        let resolved = resolve_recipient(&prefs, prefs.preferred_channel);
-        infra_repo
-            .enqueue_comms(
-                Some(user_id),
-                resolved.channel,
-                CommsType::AccountDeletion,
-                &resolved.recipient,
-                Some(&subject),
-                &body,
-                None,
-            )
-            .await
-    }
-
-    pub async fn enqueue_plc_operation(
-        user_repo: &dyn UserRepository,
-        infra_repo: &dyn InfraRepository,
-        user_id: Uuid,
-        token: &str,
-        hostname: &str,
-    ) -> Result<Uuid, DbError> {
-        let prefs = user_repo
-            .get_comms_prefs(user_id)
-            .await?
-            .ok_or(DbError::NotFound)?;
-        let strings = get_strings(prefs.preferred_locale.as_deref().unwrap_or("en"));
-        let body = format_message(
-            strings.plc_operation_body,
-            &[("handle", &prefs.handle), ("token", token)],
-        );
-        let subject = format_message(strings.plc_operation_subject, &[("hostname", hostname)]);
-        let resolved = resolve_recipient(&prefs, prefs.preferred_channel);
-        infra_repo
-            .enqueue_comms(
-                Some(user_id),
-                resolved.channel,
-                CommsType::PlcOperation,
-                &resolved.recipient,
-                Some(&subject),
-                &body,
-                None,
-            )
-            .await
-    }
-
-    pub async fn enqueue_passkey_recovery(
-        user_repo: &dyn UserRepository,
-        infra_repo: &dyn InfraRepository,
-        user_id: Uuid,
-        recovery_url: &str,
-        hostname: &str,
-    ) -> Result<Uuid, DbError> {
-        let prefs = user_repo
-            .get_comms_prefs(user_id)
-            .await?
-            .ok_or(DbError::NotFound)?;
-        let strings = get_strings(prefs.preferred_locale.as_deref().unwrap_or("en"));
-        let body = format_message(
-            strings.passkey_recovery_body,
-            &[("handle", &prefs.handle), ("url", recovery_url)],
-        );
-        let subject = format_message(strings.passkey_recovery_subject, &[("hostname", hostname)]);
-        let resolved = resolve_recipient(&prefs, prefs.preferred_channel);
-        infra_repo
-            .enqueue_comms(
-                Some(user_id),
-                resolved.channel,
-                CommsType::PasskeyRecovery,
-                &resolved.recipient,
                 Some(&subject),
                 &body,
                 None,
@@ -524,8 +456,7 @@ pub mod repo {
         user_repo: &dyn UserRepository,
         infra_repo: &dyn InfraRepository,
         user_id: Uuid,
-        channel: tranquil_db_traits::CommsChannel,
-        recipient: &str,
+        target: &VerificationTarget,
         token: &str,
         hostname: &str,
     ) -> Result<Uuid, DbError> {
@@ -533,13 +464,13 @@ pub mod repo {
             .get_comms_prefs(user_id)
             .await?
             .ok_or(DbError::NotFound)?;
-        let strings = get_strings(prefs.preferred_locale.as_deref().unwrap_or("en"));
-        let encoded_recipient = urlencoding::encode(recipient);
+        let strings = get_strings(locale_of(&prefs));
+        let encoded_id = urlencoding::encode(&target.id);
         let encoded_token = urlencoding::encode(token);
         let verify_page = format!("https://{}/app/verify", hostname);
         let verify_link = format!(
             "https://{}/app/verify?token={}&identifier={}",
-            hostname, encoded_token, encoded_recipient
+            hostname, encoded_token, encoded_id
         );
         let body = format_message(
             strings.migration_verification_body,
@@ -557,9 +488,8 @@ pub mod repo {
         infra_repo
             .enqueue_comms(
                 Some(user_id),
-                channel,
+                &target.recipient,
                 CommsType::MigrationVerification,
-                recipient,
                 Some(&subject),
                 &body,
                 None,
@@ -571,12 +501,10 @@ pub mod repo {
         user_repo: &dyn UserRepository,
         infra_repo: &dyn InfraRepository,
         user_id: Uuid,
-        channel: tranquil_db_traits::CommsChannel,
-        recipient: &str,
+        target: &VerificationTarget,
         code: &str,
         hostname: &str,
     ) -> Result<Uuid, DbError> {
-        let comms_channel = channel;
         let prefs = match user_repo.get_comms_prefs(user_id).await {
             Ok(p) => p,
             Err(e) => {
@@ -584,17 +512,14 @@ pub mod repo {
                 None
             }
         };
-        let locale = prefs
-            .as_ref()
-            .and_then(|p| p.preferred_locale.as_deref())
-            .unwrap_or("en");
+        let locale = prefs.as_ref().map(locale_of).unwrap_or("en");
         let strings = get_strings(locale);
         let encoded_token = urlencoding::encode(code);
-        let encoded_recipient = urlencoding::encode(recipient);
+        let encoded_id = urlencoding::encode(&target.id);
         let verify_page = format!("https://{}/app/verify", hostname);
         let verify_link = format!(
             "https://{}/app/verify?token={}&identifier={}",
-            hostname, encoded_token, encoded_recipient
+            hostname, encoded_token, encoded_id
         );
         let body = format_message(
             strings.signup_verification_body,
@@ -612,80 +537,8 @@ pub mod repo {
         infra_repo
             .enqueue_comms(
                 Some(user_id),
-                comms_channel,
+                &target.recipient,
                 CommsType::EmailVerification,
-                recipient,
-                Some(&subject),
-                &body,
-                None,
-            )
-            .await
-    }
-
-    pub async fn enqueue_2fa_code(
-        user_repo: &dyn UserRepository,
-        infra_repo: &dyn InfraRepository,
-        user_id: Uuid,
-        code: &str,
-        hostname: &str,
-    ) -> Result<Uuid, DbError> {
-        let prefs = user_repo
-            .get_comms_prefs(user_id)
-            .await?
-            .ok_or(DbError::NotFound)?;
-        let strings = get_strings(prefs.preferred_locale.as_deref().unwrap_or("en"));
-        let body = format_message(
-            strings.two_factor_code_body,
-            &[("handle", &prefs.handle), ("code", code)],
-        );
-        let subject = format_message(strings.two_factor_code_subject, &[("hostname", hostname)]);
-        let resolved = resolve_recipient(&prefs, prefs.preferred_channel);
-        infra_repo
-            .enqueue_comms(
-                Some(user_id),
-                resolved.channel,
-                CommsType::TwoFactorCode,
-                &resolved.recipient,
-                Some(&subject),
-                &body,
-                None,
-            )
-            .await
-    }
-
-    pub async fn enqueue_legacy_login(
-        user_repo: &dyn UserRepository,
-        infra_repo: &dyn InfraRepository,
-        user_id: Uuid,
-        hostname: &str,
-        client_ip: &str,
-        channel: tranquil_db_traits::CommsChannel,
-    ) -> Result<Uuid, DbError> {
-        let prefs = user_repo
-            .get_comms_prefs(user_id)
-            .await?
-            .ok_or(DbError::NotFound)?;
-        let strings = get_strings(prefs.preferred_locale.as_deref().unwrap_or("en"));
-        let timestamp = chrono::Utc::now()
-            .format("%Y-%m-%d %H:%M:%S UTC")
-            .to_string();
-        let body = format_message(
-            strings.legacy_login_body,
-            &[
-                ("handle", &prefs.handle),
-                ("timestamp", &timestamp),
-                ("ip", client_ip),
-                ("hostname", hostname),
-            ],
-        );
-        let subject = format_message(strings.legacy_login_subject, &[("hostname", hostname)]);
-        let resolved = resolve_recipient(&prefs, channel);
-        infra_repo
-            .enqueue_comms(
-                Some(user_id),
-                resolved.channel,
-                CommsType::LegacyLoginAlert,
-                &resolved.recipient,
                 Some(&subject),
                 &body,
                 None,
@@ -697,20 +550,19 @@ pub mod repo {
         user_repo: &dyn UserRepository,
         infra_repo: &dyn InfraRepository,
         user_id: Uuid,
-        channel: tranquil_db_traits::CommsChannel,
-        recipient: &str,
+        recipient: &Recipient,
         hostname: &str,
     ) -> Result<Uuid, DbError> {
         let prefs = user_repo
             .get_comms_prefs(user_id)
             .await?
             .ok_or(DbError::NotFound)?;
-        let strings = get_strings(prefs.preferred_locale.as_deref().unwrap_or("en"));
+        let strings = get_strings(locale_of(&prefs));
         let body = format_message(
             strings.channel_verified_body,
             &[
                 ("handle", &prefs.handle),
-                ("channel", channel.display_name()),
+                ("channel", recipient.channel().display_name()),
                 ("hostname", hostname),
             ],
         );
@@ -718,13 +570,116 @@ pub mod repo {
         infra_repo
             .enqueue_comms(
                 Some(user_id),
-                channel,
-                CommsType::ChannelVerified,
                 recipient,
+                CommsType::ChannelVerified,
                 Some(&subject),
                 &body,
                 None,
             )
             .await
     }
+
+    pub async fn try_channel_verified_notice(
+        user_repo: &dyn UserRepository,
+        infra_repo: &dyn InfraRepository,
+        user_id: Uuid,
+        recipient: &Recipient,
+        hostname: &str,
+    ) {
+        if let Err(e) =
+            enqueue_channel_verified(user_repo, infra_repo, user_id, recipient, hostname).await
+        {
+            warn!(error = %e, "Failed to enqueue channel verified notification");
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn bot_channel_recipients_fall_back_to_email() {
+        let telegram =
+            VerificationTarget::resolve(CommsChannel::Telegram, "123456789", Some("user@jola.dev"))
+                .unwrap();
+        assert_eq!(telegram.recipient.channel(), CommsChannel::Email);
+
+        let discord = VerificationTarget::resolve(
+            CommsChannel::Discord,
+            "274656283714826240",
+            Some("user@jola.dev"),
+        )
+        .unwrap();
+        assert_eq!(discord.recipient.channel(), CommsChannel::Email);
+    }
+
+    #[test]
+    fn resolution_keeps_id_for_bot_channels() {
+        let target =
+            VerificationTarget::resolve(CommsChannel::Telegram, "oys_01", Some("user@jola.dev"))
+                .unwrap();
+        assert_eq!(target.id, "oys_01");
+        assert_eq!(target.recipient.channel(), CommsChannel::Email);
+    }
+
+    #[test]
+    fn direct_channels_parse_id() {
+        let email = VerificationTarget::resolve(CommsChannel::Email, "user@nel.pet", None).unwrap();
+        assert_eq!(email.recipient.as_str(), "user@nel.pet");
+
+        let signal = VerificationTarget::resolve(CommsChannel::Signal, "oys.01", None).unwrap();
+        assert_eq!(signal.recipient.channel(), CommsChannel::Signal);
+    }
+
+    #[test]
+    fn signal_falls_back_when_id_isnt_username() {
+        let target =
+            VerificationTarget::resolve(CommsChannel::Signal, "oys", Some("user@jola.dev"))
+                .unwrap();
+        assert_eq!(target.recipient.channel(), CommsChannel::Email);
+    }
+
+    #[test]
+    fn resolve_fails_without_fallback() {
+        assert!(VerificationTarget::resolve(CommsChannel::Telegram, "oys_01", None).is_err());
+        assert!(VerificationTarget::resolve(CommsChannel::Signal, "oys", None).is_err());
+    }
+}
+
+#[cfg(test)]
+mod recipient_for_tests {
+    use super::*;
+
+    fn undeliverable_prefs() -> UserCommsPrefs {
+        UserCommsPrefs {
+            email: None,
+            handle: "oys.nel.pet".parse().unwrap(),
+            preferred_channel: CommsChannel::Telegram,
+            preferred_locale: None,
+            telegram_chat_id: None,
+            discord_id: None,
+            signal_username: None,
+        }
+    }
+
+    #[test]
+    fn undeliverable_prefs_resolve_to_none_on_every_channel() {
+        let prefs = undeliverable_prefs();
+        assert_eq!(recipient_for(&prefs, CommsChannel::Telegram), None);
+        assert_eq!(recipient_for(&prefs, CommsChannel::Email), None);
+    }
+
+    #[test]
+    fn zero_chat_id_falls_back_to_email() {
+        let prefs = UserCommsPrefs {
+            telegram_chat_id: Some(0),
+            email: Some("oys@jola.dev".into()),
+            ..undeliverable_prefs()
+        };
+        assert_eq!(
+            recipient_for(&prefs, CommsChannel::Telegram),
+            Some(Recipient::Email(EmailAddress::new("oys@jola.dev").unwrap()))
+        );
+    }
 }

crates/tranquil-pds/tests/account_notifications.rs

@@ -1,8 +1,54 @@
 mod common;
-use common::{base_url, client, create_account_and_login, get_test_repos};
+use common::{base_url, client, create_account_and_login, get_test_repos, user_id_of};
 use serde_json::{Value, json};
 use tranquil_db_traits::{CommsChannel, CommsType};
-use tranquil_types::Did;
+use tranquil_types::{Did, Recipient};
+
+type Repos = tranquil_db::PostgresRepositories;
+
+async fn set_prefs(
+    client: &reqwest::Client,
+    base: &str,
+    token: &str,
+    prefs: serde_json::Value,
+) -> reqwest::Response {
+    client
+        .post(format!("{}/xrpc/_account.updateNotificationPrefs", base))
+        .header("Authorization", format!("Bearer {}", token))
+        .json(&prefs)
+        .send()
+        .await
+        .unwrap()
+}
+
+async fn confirm_channel(
+    client: &reqwest::Client,
+    base: &str,
+    token: &str,
+    channel: &str,
+    id: &str,
+    code: &str,
+) -> reqwest::Response {
+    client
+        .post(format!("{}/xrpc/_account.confirmChannelVerification", base))
+        .header("Authorization", format!("Bearer {}", token))
+        .json(&json!({"channel": channel, "identifier": id, "code": code}))
+        .send()
+        .await
+        .unwrap()
+}
+
+async fn latest_notices(
+    repos: &Repos,
+    user_id: uuid::Uuid,
+    n: i64,
+) -> Vec<tranquil_db_traits::QueuedComms> {
+    repos
+        .infra
+        .get_latest_comms_for_user(user_id, CommsType::ChannelVerified, n)
+        .await
+        .expect("DB error")
+}
 
 #[tokio::test]
 async fn test_get_notification_history() {
@@ -11,21 +57,15 @@ async fn test_get_notification_history() {
     let repos = get_test_repos().await;
     let (token, did) = create_account_and_login(&client).await;
 
-    let user_id = repos
-        .user
-        .get_id_by_did(&Did::new(did).unwrap())
-        .await
-        .expect("DB error")
-        .expect("User not found");
+    let user_id = user_id_of(repos, &Did::new(did).unwrap()).await;
 
     for i in 0..3 {
         repos
             .infra
             .enqueue_comms(
                 Some(user_id),
-                CommsChannel::Email,
+                &Recipient::new(CommsChannel::Email, "test@nel.pet").unwrap(),
                 CommsType::Welcome,
-                "test@example.com",
                 Some(&format!("Subject {}", i)),
                 &format!("Body {}", i),
                 None,
@@ -57,16 +97,13 @@ async fn test_verify_channel_discord() {
     let base = base_url().await;
     let (token, _did) = create_account_and_login(&client).await;
 
-    let prefs = json!({
-        "discordUsername": "testuser123"
-    });
-    let resp = client
-        .post(format!("{}/xrpc/_account.updateNotificationPrefs", base))
-        .header("Authorization", format!("Bearer {}", token))
-        .json(&prefs)
-        .send()
-        .await
-        .unwrap();
+    let resp = set_prefs(
+        &client,
+        base,
+        &token,
+        json!({ "discordUsername": "testuser123" }),
+    )
+    .await;
     assert_eq!(resp.status(), 200);
     let body: Value = resp.json().await.unwrap();
     assert!(
@@ -93,51 +130,112 @@ async fn test_verify_channel_invalid_code() {
     let base = base_url().await;
     let (token, _did) = create_account_and_login(&client).await;
 
-    let prefs = json!({
-        "telegramUsername": "testuser"
-    });
-    let resp = client
-        .post(format!("{}/xrpc/_account.updateNotificationPrefs", base))
-        .header("Authorization", format!("Bearer {}", token))
-        .json(&prefs)
-        .send()
-        .await
-        .unwrap();
+    let resp = set_prefs(
+        &client,
+        base,
+        &token,
+        json!({ "telegramUsername": "testuser" }),
+    )
+    .await;
     assert_eq!(resp.status(), 200);
 
-    let input = json!({
-        "channel": "telegram",
-        "identifier": "testuser",
-        "code": "XXXX-XXXX-XXXX-XXXX"
-    });
-    let resp = client
-        .post(format!("{}/xrpc/_account.confirmChannelVerification", base))
-        .header("Authorization", format!("Bearer {}", token))
-        .json(&input)
-        .send()
-        .await
-        .unwrap();
+    let resp = confirm_channel(
+        &client,
+        base,
+        &token,
+        "telegram",
+        "testuser",
+        "XXXX-XXXX-XXXX-XXXX",
+    )
+    .await;
     assert_eq!(resp.status(), 400);
 }
 
+#[tokio::test]
+async fn test_channel_verified_notice_delivers_over_email_until_chat_id_is_stored() {
+    let client = client();
+    let base = base_url().await;
+    let repos = get_test_repos().await;
+    let (token, did) = create_account_and_login(&client).await;
+    let did = Did::new(did).unwrap();
+    let user_id = user_id_of(repos, &did).await;
+
+    let id = "10987654321";
+    let resp = set_prefs(&client, base, &token, json!({ "telegramUsername": id })).await;
+    assert_eq!(resp.status(), 200);
+
+    let code = |did: &Did| {
+        tranquil_pds::auth::verification_token::generate_channel_update_token(
+            did,
+            CommsChannel::Telegram,
+            id,
+        )
+    };
+    let resp = confirm_channel(&client, base, &token, "telegram", id, &code(&did)).await;
+    assert_eq!(resp.status(), 200);
+
+    let snapshot = |notices: &[tranquil_db_traits::QueuedComms]| {
+        notices
+            .iter()
+            .map(|notice| (notice.channel, notice.recipient.clone()))
+            .collect::<Vec<_>>()
+    };
+    let notices = latest_notices(repos, user_id, 5).await;
+    assert!(
+        notices
+            .iter()
+            .all(|notice| notice.channel != CommsChannel::Telegram),
+        "Telegram identifier entered the queue as a chat ID: {:?}",
+        snapshot(&notices)
+    );
+    assert!(
+        notices
+            .iter()
+            .any(|notice| notice.channel == CommsChannel::Email),
+        "The notice should fall back to email: {:?}",
+        snapshot(&notices)
+    );
+
+    repos
+        .user
+        .store_telegram_chat_id(
+            &tranquil_types::TelegramUsername::new(id).unwrap(),
+            10987654321,
+            None,
+        )
+        .await
+        .expect("DB error")
+        .expect("The Telegram username didn't match a user");
+
+    let resp = confirm_channel(&client, base, &token, "telegram", id, &code(&did)).await;
+    assert_eq!(resp.status(), 200);
+
+    let notices = latest_notices(repos, user_id, 10).await;
+    assert!(
+        notices
+            .iter()
+            .any(|notice| notice.channel == CommsChannel::Telegram
+                && notice.recipient == "10987654321"),
+        "A stored chat ID should receive the notice: {:?}",
+        snapshot(&notices)
+    );
+}
+
 #[tokio::test]
 async fn test_verify_channel_not_set() {
     let client = client();
     let base = base_url().await;
     let (token, _did) = create_account_and_login(&client).await;
 
-    let input = json!({
-        "channel": "signal",
-        "identifier": "123456",
-        "code": "XXXX-XXXX-XXXX-XXXX"
-    });
-    let resp = client
-        .post(format!("{}/xrpc/_account.confirmChannelVerification", base))
-        .header("Authorization", format!("Bearer {}", token))
-        .json(&input)
-        .send()
-        .await
-        .unwrap();
+    let resp = confirm_channel(
+        &client,
+        base,
+        &token,
+        "signal",
+        "123456",
+        "XXXX-XXXX-XXXX-XXXX",
+    )
+    .await;
     assert_eq!(resp.status(), 400);
 }
 
@@ -148,17 +246,8 @@ async fn test_update_email_via_notification_prefs() {
     let repos = get_test_repos().await;
     let (token, did) = create_account_and_login(&client).await;
 
-    let unique_email = format!("newemail_{}@example.com", uuid::Uuid::new_v4());
-    let prefs = json!({
-        "email": unique_email
-    });
-    let resp = client
-        .post(format!("{}/xrpc/_account.updateNotificationPrefs", base))
-        .header("Authorization", format!("Bearer {}", token))
-        .json(&prefs)
-        .send()
-        .await
-        .unwrap();
+    let unique_email = format!("newemail_{}@jola.dev", uuid::Uuid::new_v4());
+    let resp = set_prefs(&client, base, &token, json!({ "email": unique_email })).await;
     assert_eq!(resp.status(), 200);
     let body: Value = resp.json().await.unwrap();
     assert!(
@@ -168,12 +257,7 @@ async fn test_update_email_via_notification_prefs() {
             .contains(&json!("email"))
     );
 
-    let user_id = repos
-        .user
-        .get_id_by_did(&Did::new(did).unwrap())
-        .await
-        .expect("DB error")
-        .expect("User not found");
+    let user_id = user_id_of(repos, &Did::new(did).unwrap()).await;
 
     let comms = repos
         .infra
@@ -202,18 +286,7 @@ async fn test_update_email_via_notification_prefs() {
                 .unwrap_or_default()
         });
 
-    let input = json!({
-        "channel": "email",
-        "identifier": unique_email,
-        "code": code
-    });
-    let resp = client
-        .post(format!("{}/xrpc/_account.confirmChannelVerification", base))
-        .header("Authorization", format!("Bearer {}", token))
-        .json(&input)
-        .send()
-        .await
-        .unwrap();
+    let resp = confirm_channel(&client, base, &token, "email", &unique_email, &code).await;
     assert_eq!(resp.status(), 200);
 
     let resp = client

crates/tranquil-pds/tests/admin_email.rs

@@ -16,7 +16,7 @@ async fn test_send_email_success() {
         .bearer_auth(&access_jwt)
         .json(&json!({
             "recipientDid": did,
-            "senderDid": "did:plc:admin",
+            "senderDid": "did:plc:oystercafe",
             "content": "Hello, this is a test email from the admin.",
             "subject": "Test Admin Email"
         }))
@@ -26,12 +26,7 @@ async fn test_send_email_success() {
     assert_eq!(res.status(), StatusCode::OK);
     let body: Value = res.json().await.expect("Invalid JSON");
     assert_eq!(body["sent"], true);
-    let user_id = repos
-        .user
-        .get_id_by_did(&Did::new(did).unwrap())
-        .await
-        .expect("DB error")
-        .expect("User not found");
+    let user_id = common::user_id_of(repos, &Did::new(did).unwrap()).await;
     let comms = repos
         .infra
         .get_latest_comms_for_user(user_id, CommsType::AdminEmail, 1)
@@ -57,7 +52,7 @@ async fn test_send_email_default_subject() {
         .bearer_auth(&access_jwt)
         .json(&json!({
             "recipientDid": did,
-            "senderDid": "did:plc:admin",
+            "senderDid": "did:plc:oystercafe",
             "content": "Email without subject"
         }))
         .send()
@@ -66,12 +61,7 @@ async fn test_send_email_default_subject() {
     assert_eq!(res.status(), StatusCode::OK);
     let body: Value = res.json().await.expect("Invalid JSON");
     assert_eq!(body["sent"], true);
-    let user_id = repos
-        .user
-        .get_id_by_did(&Did::new(did).unwrap())
-        .await
-        .expect("DB error")
-        .expect("User not found");
+    let user_id = common::user_id_of(repos, &Did::new(did).unwrap()).await;
     let comms = repos
         .infra
         .get_latest_comms_for_user(user_id, CommsType::AdminEmail, 10)
@@ -101,7 +91,7 @@ async fn test_send_email_recipient_not_found() {
         .bearer_auth(&access_jwt)
         .json(&json!({
             "recipientDid": "did:plc:nonexistent",
-            "senderDid": "did:plc:admin",
+            "senderDid": "did:plc:oystercafe",
             "content": "Test content"
         }))
         .send()
@@ -122,7 +112,7 @@ async fn test_send_email_missing_content() {
         .bearer_auth(&access_jwt)
         .json(&json!({
             "recipientDid": did,
-            "senderDid": "did:plc:admin",
+            "senderDid": "did:plc:oystercafe",
             "content": ""
         }))
         .send()
@@ -143,7 +133,7 @@ async fn test_send_email_missing_recipient() {
         .bearer_auth(&access_jwt)
         .json(&json!({
             "recipientDid": "",
-            "senderDid": "did:plc:admin",
+            "senderDid": "did:plc:oystercafe",
             "content": "Test content"
         }))
         .send()
@@ -160,7 +150,7 @@ async fn test_send_email_requires_auth() {
         .post(format!("{}/xrpc/com.atproto.admin.sendEmail", base_url))
         .json(&json!({
             "recipientDid": "did:plc:test",
-            "senderDid": "did:plc:admin",
+            "senderDid": "did:plc:oystercafe",
             "content": "Test content"
         }))
         .send()
@@ -168,3 +158,39 @@ async fn test_send_email_requires_auth() {
         .expect("Failed to send email");
     assert_eq!(res.status(), StatusCode::UNAUTHORIZED);
 }
+
+#[tokio::test]
+async fn test_send_email_rejects_garbage_stored_email() {
+    let client = common::client();
+    let base_url = common::base_url().await;
+    let repos = common::get_test_repos().await;
+    let (access_jwt, did) = common::create_admin_account_and_login(&client).await;
+    let user_id = common::user_id_of(repos, &Did::new(did.clone()).unwrap()).await;
+    repos
+        .user
+        .update_email(user_id, "not-an-email")
+        .await
+        .expect("DB error");
+
+    let res = client
+        .post(format!("{}/xrpc/com.atproto.admin.sendEmail", base_url))
+        .bearer_auth(&access_jwt)
+        .json(&json!({
+            "recipientDid": did,
+            "content": "This email should never go out"
+        }))
+        .send()
+        .await
+        .expect("Failed to send email");
+    assert_eq!(res.status(), StatusCode::BAD_REQUEST);
+
+    let comms = repos
+        .infra
+        .get_latest_comms_for_user(user_id, CommsType::AdminEmail, 1)
+        .await
+        .expect("DB error");
+    assert!(
+        comms.is_empty(),
+        "A garbage stored email doesn't reach the queue"
+    );
+}

crates/tranquil-pds/tests/common/mod.rs

@@ -586,6 +586,8 @@ async fn spawn_server(config: ServerConfig) -> ServerInstance {
     TEST_BLOCK_STORE.set(state.block_store.clone()).ok();
     if let Some((cache, distributed_rate_limiter)) = config.cache {
         state = state.with_cache(cache, distributed_rate_limiter);
+    } else {
+        tranquil_pds::state::set_rate_limiting_disabled(true);
     }
     TEST_APP_STATE.set(state.clone()).ok();
     tranquil_sync::listener::start_sequencer_listener(state.clone()).await;
@@ -924,6 +926,19 @@ pub async fn get_test_repos() -> &'static Arc<tranquil_db::PostgresRepositories>
     TEST_REPOS.get().expect("TEST_REPOS not initialized")
 }
 
+#[allow(dead_code)]
+pub async fn user_id_of(
+    repos: &tranquil_db::PostgresRepositories,
+    did: &tranquil_types::Did,
+) -> uuid::Uuid {
+    repos
+        .user
+        .get_id_by_did(did)
+        .await
+        .expect("DB error")
+        .expect("User not found")
+}
+
 #[allow(dead_code)]
 pub async fn get_test_block_store() -> &'static tranquil_pds::repo::AnyBlockStore {
     base_url().await;

crates/tranquil-pds/tests/email_update.rs

@@ -69,7 +69,7 @@ async fn test_request_email_update_returns_token_required() {
     let client = common::client();
     let base_url = common::base_url().await;
     let handle = format!("er{}", &uuid::Uuid::new_v4().simple().to_string()[..12]);
-    let email = format!("{}@example.com", handle);
+    let email = format!("{}@nel.pet", handle);
     let (access_jwt, _) = create_verified_account(&client, base_url, &handle, &email).await;
 
     let res = client
@@ -92,9 +92,9 @@ async fn test_update_email_flow_success() {
     let base_url = common::base_url().await;
     let repos = common::get_test_repos().await;
     let handle = format!("eu{}", &uuid::Uuid::new_v4().simple().to_string()[..12]);
-    let email = format!("{}@example.com", handle);
+    let email = format!("{}@nel.pet", handle);
     let (access_jwt, did) = create_verified_account(&client, base_url, &handle, &email).await;
-    let new_email = format!("new_{}@example.com", handle);
+    let new_email = format!("new_{}@jola.dev", handle);
 
     let res = client
         .post(format!(
@@ -139,9 +139,9 @@ async fn test_update_email_requires_token_when_verified() {
     let client = common::client();
     let base_url = common::base_url().await;
     let handle = format!("ed{}", &uuid::Uuid::new_v4().simple().to_string()[..12]);
-    let email = format!("{}@example.com", handle);
+    let email = format!("{}@nel.pet", handle);
     let (access_jwt, _) = create_verified_account(&client, base_url, &handle, &email).await;
-    let new_email = format!("direct_{}@example.com", handle);
+    let new_email = format!("direct_{}@jola.dev", handle);
 
     let res = client
         .post(format!("{}/xrpc/com.atproto.server.updateEmail", base_url))
@@ -160,7 +160,7 @@ async fn test_update_email_same_email_noop() {
     let client = common::client();
     let base_url = common::base_url().await;
     let handle = format!("es{}", &uuid::Uuid::new_v4().simple().to_string()[..12]);
-    let email = format!("{}@example.com", handle);
+    let email = format!("{}@nel.pet", handle);
     let (access_jwt, _) = create_verified_account(&client, base_url, &handle, &email).await;
 
     let res = client
@@ -182,9 +182,9 @@ async fn test_update_email_invalid_token() {
     let client = common::client();
     let base_url = common::base_url().await;
     let handle = format!("eb{}", &uuid::Uuid::new_v4().simple().to_string()[..12]);
-    let email = format!("{}@example.com", handle);
+    let email = format!("{}@nel.pet", handle);
     let (access_jwt, _) = create_verified_account(&client, base_url, &handle, &email).await;
-    let new_email = format!("badtok_{}@example.com", handle);
+    let new_email = format!("badtok_{}@jola.dev", handle);
 
     let res = client
         .post(format!(
@@ -219,7 +219,7 @@ async fn test_update_email_no_auth() {
 
     let res = client
         .post(format!("{}/xrpc/com.atproto.server.updateEmail", base_url))
-        .json(&json!({ "email": "test@example.com" }))
+        .json(&json!({ "email": "test@jola.dev" }))
         .send()
         .await
         .expect("Failed to send request");
@@ -233,7 +233,7 @@ async fn test_update_email_invalid_format() {
     let client = common::client();
     let base_url = common::base_url().await;
     let handle = format!("ef{}", &uuid::Uuid::new_v4().simple().to_string()[..12]);
-    let email = format!("{}@example.com", handle);
+    let email = format!("{}@nel.pet", handle);
     let (access_jwt, _) = create_verified_account(&client, base_url, &handle, &email).await;
 
     let res = client
@@ -252,7 +252,7 @@ async fn test_confirm_email_confirms_existing_email() {
     let base_url = common::base_url().await;
     let repos = common::get_test_repos().await;
     let handle = format!("ec{}", &uuid::Uuid::new_v4().simple().to_string()[..12]);
-    let email = format!("{}@example.com", handle);
+    let email = format!("{}@nel.pet", handle);
 
     let res = client
         .post(format!(
@@ -327,7 +327,7 @@ async fn test_confirm_email_rejects_wrong_email() {
     let base_url = common::base_url().await;
     let repos = common::get_test_repos().await;
     let handle = format!("ew{}", &uuid::Uuid::new_v4().simple().to_string()[..12]);
-    let email = format!("{}@example.com", handle);
+    let email = format!("{}@jola.dev", handle);
 
     let res = client
         .post(format!(
@@ -378,7 +378,7 @@ async fn test_confirm_email_rejects_wrong_email() {
         .post(format!("{}/xrpc/com.atproto.server.confirmEmail", base_url))
         .bearer_auth(&access_jwt)
         .json(&json!({
-            "email": "different@example.com",
+            "email": "different@jola.dev",
             "token": code
         }))
         .send()
@@ -394,7 +394,7 @@ async fn test_confirm_email_invalid_token() {
     let client = common::client();
     let base_url = common::base_url().await;
     let handle = format!("ei{}", &uuid::Uuid::new_v4().simple().to_string()[..12]);
-    let email = format!("{}@example.com", handle);
+    let email = format!("{}@jola.dev", handle);
 
     let res = client
         .post(format!(
@@ -437,7 +437,7 @@ async fn test_unverified_account_can_update_email_without_token() {
     let base_url = common::base_url().await;
     let repos = common::get_test_repos().await;
     let handle = format!("ev{}", &uuid::Uuid::new_v4().simple().to_string()[..12]);
-    let email = format!("{}@example.com", handle);
+    let email = format!("{}@nel.pet", handle);
 
     let res = client
         .post(format!(
@@ -473,10 +473,10 @@ async fn test_unverified_account_can_update_email_without_token() {
     let body: Value = res.json().await.expect("Invalid JSON");
     assert_eq!(
         body["tokenRequired"], false,
-        "Unverified account should not require token"
+        "An unverified account shouldn't require a token"
     );
 
-    let new_email = format!("new_{}@example.com", handle);
+    let new_email = format!("new_{}@jola.dev", handle);
     let res = client
         .post(format!("{}/xrpc/com.atproto.server.updateEmail", base_url))
         .bearer_auth(&access_jwt)
@@ -508,11 +508,11 @@ async fn test_update_email_to_same_as_another_user_allowed() {
     let repos = common::get_test_repos().await;
 
     let handle1 = format!("d1{}", &uuid::Uuid::new_v4().simple().to_string()[..12]);
-    let email1 = format!("{}@example.com", handle1);
+    let email1 = format!("{}@jola.dev", handle1);
     let (_, _) = create_verified_account(&client, base_url, &handle1, &email1).await;
 
     let handle2 = format!("d2{}", &uuid::Uuid::new_v4().simple().to_string()[..12]);
-    let email2 = format!("{}@example.com", handle2);
+    let email2 = format!("{}@jola.dev", handle2);
     let (access_jwt2, did2) = create_verified_account(&client, base_url, &handle2, &email2).await;
 
     let res = client
@@ -554,3 +554,29 @@ async fn test_update_email_to_same_as_another_user_allowed() {
         .email;
     assert_eq!(user_email, Some(email1.clone()));
 }
+
+#[tokio::test]
+async fn test_check_email_in_use_distinguishes_empty_from_invalid() {
+    let client = common::client();
+    let base = common::base_url().await;
+
+    let resp = client
+        .post(format!("{}/xrpc/_account.checkEmailInUse", base))
+        .json(&json!({ "email": "not-an-email" }))
+        .send()
+        .await
+        .unwrap();
+    assert_eq!(resp.status(), StatusCode::BAD_REQUEST);
+    let body: Value = resp.json().await.unwrap();
+    assert_eq!(body["message"], "Invalid email address");
+
+    let resp = client
+        .post(format!("{}/xrpc/_account.checkEmailInUse", base))
+        .json(&json!({ "email": "   " }))
+        .send()
+        .await
+        .unwrap();
+    assert_eq!(resp.status(), StatusCode::BAD_REQUEST);
+    let body: Value = resp.json().await.unwrap();
+    assert_eq!(body["message"], "Email is required");
+}

crates/tranquil-pds/tests/gc_after_delete.rs

@@ -15,12 +15,7 @@ async fn test_delete_record_marks_blocks_obsolete() {
     let (did, jwt) = setup_new_user("gc-after-delete").await;
     let did = Did::new(did).expect("setup_new_user returned a valid DID");
 
-    let user_id = repos
-        .user
-        .get_id_by_did(&did)
-        .await
-        .expect("DB error")
-        .expect("User not found");
+    let user_id = user_id_of(repos, &did).await;
 
     let collection = Nsid::new("app.bsky.feed.post".to_string()).expect("valid NSID");
     let rkey = Rkey::new(format!("gc_test_{}", Utc::now().timestamp_millis())).expect("valid rkey");
@@ -110,12 +105,7 @@ async fn test_update_record_marks_old_record_block_obsolete() {
     let (did, jwt) = setup_new_user("gc-after-update").await;
     let did = Did::new(did).expect("setup_new_user returned a valid DID");
 
-    let user_id = repos
-        .user
-        .get_id_by_did(&did)
-        .await
-        .expect("DB error")
-        .expect("User not found");
+    let user_id = user_id_of(repos, &did).await;
 
     let collection = Nsid::new("app.bsky.feed.post".to_string()).expect("valid NSID");
     let rkey =

crates/tranquil-pds/tests/legacy_2fa.rs

@@ -1,9 +1,9 @@
 mod common;
 
-use common::{base_url, client, create_account_and_login, get_test_repos};
+use common::{base_url, client, create_account_and_login, get_test_repos, user_id_of};
 use reqwest::StatusCode;
 use serde_json::{Value, json};
-use tranquil_db_traits::CommsType;
+use tranquil_db_traits::{CommsChannel, CommsType};
 use tranquil_types::Did;
 
 async fn enable_totp_for_user(did: &str) {
@@ -26,13 +26,7 @@ async fn set_allow_legacy_login(did: &str, allow: bool) {
 
 async fn get_2fa_code_from_queue(did: &str) -> Option<String> {
     let repos = get_test_repos().await;
-    let parsed_did = Did::new(did.to_string()).unwrap();
-    let user_id = repos
-        .user
-        .get_id_by_did(&parsed_did)
-        .await
-        .expect("DB error")
-        .expect("User not found");
+    let user_id = user_id_of(repos, &Did::new(did).unwrap()).await;
 
     let comms = repos
         .infra
@@ -56,13 +50,7 @@ async fn get_2fa_code_from_queue(did: &str) -> Option<String> {
 
 async fn clear_2fa_challenges_for_user(did: &str) {
     let repos = get_test_repos().await;
-    let parsed_did = Did::new(did.to_string()).unwrap();
-    let user_id = repos
-        .user
-        .get_id_by_did(&parsed_did)
-        .await
-        .expect("DB error")
-        .expect("User not found");
+    let user_id = user_id_of(repos, &Did::new(did).unwrap()).await;
 
     let _ = repos
         .infra
@@ -72,13 +60,7 @@ async fn clear_2fa_challenges_for_user(did: &str) {
 
 async fn set_email_auth_factor(did: &str, enabled: bool) {
     let repos = get_test_repos().await;
-    let parsed_did = Did::new(did.to_string()).unwrap();
-    let user_id = repos
-        .user
-        .get_id_by_did(&parsed_did)
-        .await
-        .expect("DB error")
-        .expect("User not found");
+    let user_id = user_id_of(repos, &Did::new(did).unwrap()).await;
 
     repos
         .infra
@@ -131,6 +113,55 @@ async fn test_legacy_2fa_auth_factor_required() {
     );
 }
 
+#[tokio::test]
+async fn test_legacy_2fa_undeliverable_channel_fails_login() {
+    let client = client();
+    let base = base_url().await;
+    let repos = get_test_repos().await;
+    let (_token, did) = create_account_and_login(&client).await;
+
+    enable_totp_for_user(&did).await;
+    set_allow_legacy_login(&did, true).await;
+    let parsed_did = Did::new(did.clone()).unwrap();
+    repos
+        .user
+        .set_channel_verified(&parsed_did, CommsChannel::Discord)
+        .await
+        .expect("DB error");
+    let user_id = user_id_of(repos, &parsed_did).await;
+    repos
+        .user
+        .update_email(user_id, &format!("undeliverable-{}", uuid::Uuid::new_v4()))
+        .await
+        .expect("DB error");
+
+    let handle = get_handle(&did).await;
+    let resp = client
+        .post(format!("{}/xrpc/com.atproto.server.createSession", base))
+        .json(&json!({
+            "identifier": handle,
+            "password": "Testpass123!"
+        }))
+        .send()
+        .await
+        .unwrap();
+
+    assert_eq!(resp.status(), StatusCode::BAD_REQUEST);
+    let body: Value = resp.json().await.unwrap();
+    assert_eq!(body["error"], "InvalidRequest");
+    assert!(
+        body["message"]
+            .as_str()
+            .unwrap_or("")
+            .contains("couldn't deliver the verification code"),
+        "the response should say the code couldn't be delivered: {body}"
+    );
+    assert!(
+        get_2fa_code_from_queue(&did).await.is_none(),
+        "the comms queue should stay empty for this user"
+    );
+}
+
 #[tokio::test]
 async fn test_legacy_2fa_valid_code_succeeds() {
     let client = client();

crates/tranquil-pds/tests/notifications.rs

@@ -1,24 +1,18 @@
 mod common;
 use tranquil_db_traits::{CommsChannel, CommsStatus, CommsType};
-use tranquil_types::Did;
+use tranquil_types::{Did, Recipient};
 
 #[tokio::test]
 async fn test_enqueue_comms() {
     let repos = common::get_test_repos().await;
     let (_, did) = common::create_account_and_login(&common::client()).await;
-    let user_id = repos
-        .user
-        .get_id_by_did(&Did::new(did).unwrap())
-        .await
-        .expect("DB error")
-        .expect("User not found");
+    let user_id = common::user_id_of(repos, &Did::new(did).unwrap()).await;
     repos
         .infra
         .enqueue_comms(
             Some(user_id),
-            CommsChannel::Email,
+            &Recipient::new(CommsChannel::Email, "test@nel.pet").unwrap(),
             CommsType::Welcome,
-            "test@example.com",
             Some("Test Subject"),
             "Test body",
             None,
@@ -32,7 +26,7 @@ async fn test_enqueue_comms() {
         .expect("DB error");
     let row = comms.first().expect("Comms not found");
     assert_eq!(row.user_id, Some(user_id));
-    assert_eq!(row.recipient, "test@example.com");
+    assert_eq!(row.recipient, "test@nel.pet");
     assert_eq!(row.subject.as_deref(), Some("Test Subject"));
     assert_eq!(row.body, "Test body");
     assert_eq!(row.channel, CommsChannel::Email);
@@ -44,26 +38,20 @@ async fn test_enqueue_comms() {
 async fn test_comms_queue_status_index() {
     let repos = common::get_test_repos().await;
     let (_, did) = common::create_account_and_login(&common::client()).await;
-    let user_id = repos
-        .user
-        .get_id_by_did(&Did::new(did).unwrap())
-        .await
-        .expect("DB error")
-        .expect("User not found");
+    let user_id = common::user_id_of(repos, &Did::new(did).unwrap()).await;
     let initial_count = repos
         .infra
         .count_comms_by_type(user_id, CommsType::PasswordReset)
         .await
         .expect("Failed to count");
     for i in 0..5 {
-        let recipient = format!("test{}@example.com", i);
+        let recipient = format!("test{}@jola.dev", i);
         repos
             .infra
             .enqueue_comms(
                 Some(user_id),
-                CommsChannel::Email,
+                &Recipient::new(CommsChannel::Email, &recipient).unwrap(),
                 CommsType::PasswordReset,
-                &recipient,
                 Some("Test"),
                 "Body",
                 None,

crates/tranquil-pds/tests/repair_leaf_loss.rs

@@ -57,12 +57,7 @@ async fn repair_fails_loud_on_missing_leaf_block() {
         res.text().await
     );
 
-    let user_id = repos
-        .user
-        .get_id_by_did(&Did::new(did.clone()).unwrap())
-        .await
-        .expect("DB error")
-        .expect("user not found");
+    let user_id = user_id_of(repos, &Did::new(did.clone()).unwrap()).await;
 
     let root_str = repos
         .repo

crates/tranquil-pds/tests/repo_batch.rs

@@ -498,14 +498,7 @@ async fn test_apply_writes_create_then_delete_same_rkey() {
 }
 
 async fn repo_id_for_did(did: &str) -> uuid::Uuid {
-    let repos = get_test_repos().await;
-    let parsed = Did::new(did).expect("valid did");
-    repos
-        .user
-        .get_id_by_did(&parsed)
-        .await
-        .expect("lookup user_id")
-        .expect("user exists")
+    user_id_of(get_test_repos().await, &Did::new(did).expect("valid DID")).await
 }
 
 async fn follow_uris_pointing_to(repo_id: uuid::Uuid, target_did: &str) -> Vec<String> {

crates/tranquil-pds/tests/security_fixes.rs

@@ -1,5 +1,5 @@
 mod common;
-use tranquil_pds::comms::{SendError, is_valid_phone_number, is_valid_signal_username};
+use tranquil_pds::comms::{SendError, is_valid_phone_number};
 use tranquil_pds::image::{ImageError, ImageProcessor};
 
 #[test]
@@ -46,48 +46,6 @@ fn test_phone_number_validation() {
     }
 }
 
-#[test]
-fn test_signal_username_validation() {
-    assert!(is_valid_signal_username("alice.01"));
-    assert!(is_valid_signal_username("bob_smith.99"));
-    assert!(is_valid_signal_username("user123.42"));
-    assert!(is_valid_signal_username("lu1.01"));
-    assert!(is_valid_signal_username("a_very_long_username_here.55"));
-    assert!(is_valid_signal_username("alice.123"));
-    assert!(is_valid_signal_username("alice.999999999"));
-    assert!(is_valid_signal_username("alice.18446744073709551615"));
-
-    assert!(!is_valid_signal_username("alice"));
-    assert!(!is_valid_signal_username("alice.1"));
-    assert!(!is_valid_signal_username("alice.001"));
-    assert!(!is_valid_signal_username("abc.00"));
-    assert!(!is_valid_signal_username("alice.0"));
-    assert!(!is_valid_signal_username("alice.999999999999999999999"));
-    assert!(!is_valid_signal_username(".01"));
-    assert!(!is_valid_signal_username("ab.01"));
-    assert!(!is_valid_signal_username(""));
-    assert!(!is_valid_signal_username("1alice.01"));
-    assert!(!is_valid_signal_username("alice!.01"));
-    assert!(!is_valid_signal_username("alice .01"));
-
-    assert!(!is_valid_signal_username("a".repeat(33).as_str()));
-
-    [
-        "alice.01; rm -rf /",
-        "bob.01 && cat /etc/passwd",
-        "user.01`id`",
-        "test.01$(whoami)",
-    ]
-    .iter()
-    .for_each(|malicious| {
-        assert!(
-            !is_valid_signal_username(malicious),
-            "Command injection '{}' should be rejected",
-            malicious
-        );
-    });
-}
-
 #[test]
 fn test_image_file_size_limits() {
     let processor = ImageProcessor::new();

crates/tranquil-pds/tests/sso.rs

@@ -3,7 +3,7 @@ mod common;
 use common::{base_url, client, create_account_and_login, get_test_repos};
 use reqwest::StatusCode;
 use serde_json::{Value, json};
-use tranquil_db_traits::{CommsChannel, SsoAction, SsoProviderType};
+use tranquil_db_traits::{CommsChannel, CommsType, SsoAction, SsoProviderType};
 use tranquil_oauth::{
     AuthorizationRequestParameters, CodeChallengeMethod, RequestData, ResponseType,
 };
@@ -781,6 +781,7 @@ async fn test_sso_complete_registration_multichannel_discord() {
         .json(&json!({
             "token": token,
             "handle": handle_prefix,
+            "email": "sso_discord_reg@jola.dev",
             "verification_channel": "discord",
             "discord_username": discord_id
         }))
@@ -810,6 +811,14 @@ async fn test_sso_complete_registration_multichannel_discord() {
     let user = user.unwrap();
     assert_eq!(user.channel, CommsChannel::Discord);
     assert_eq!(user.discord_username.as_deref(), Some(discord_id));
+    let quered = repos
+        .infra
+        .get_latest_comms_for_user(user.id, CommsType::EmailVerification, 1)
+        .await
+        .unwrap();
+    let comms = quered.first().expect("We queued up a verification email");
+    assert_eq!(comms.channel, CommsChannel::Email);
+    assert_eq!(comms.recipient, "sso_discord_reg@jola.dev");
 }
 
 #[tokio::test]

crates/tranquil-pds/tests/store_parity.rs

@@ -4,7 +4,7 @@ mod helpers;
 use std::sync::Arc;
 use tranquil_db::PostgresRepositories;
 use tranquil_db_traits::{Backlink, BacklinkPath, CommsChannel, CommsType};
-use tranquil_types::{AtUri, CidLink, Did, Handle, Nsid, Rkey, Tid};
+use tranquil_types::{AtUri, CidLink, Did, Handle, Nsid, Recipient, Rkey, Tid};
 use uuid::Uuid;
 
 async fn create_store_repos() -> Arc<PostgresRepositories> {
@@ -1199,9 +1199,8 @@ async fn parity_comms_queue() {
         f.pg.infra
             .enqueue_comms(
                 Some(pg_uid),
-                CommsChannel::Email,
+                &Recipient::new(CommsChannel::Email, "test@jola.dev").unwrap(),
                 CommsType::Welcome,
-                "test@example.com",
                 Some("Welcome"),
                 "Welcome body",
                 None,
@@ -1214,9 +1213,8 @@ async fn parity_comms_queue() {
         .infra
         .enqueue_comms(
             Some(store_uid),
-            CommsChannel::Email,
+            &Recipient::new(CommsChannel::Email, "test@jola.dev").unwrap(),
             CommsType::Welcome,
-            "test@example.com",
             Some("Welcome"),
             "Welcome body",
             None,

crates/tranquil-pds/tests/user_blocks_reachability.rs

@@ -109,13 +109,7 @@ async fn assert_record_gone(did: &Did, rkey: &Rkey) {
 }
 
 async fn user_id_for(did: &Did) -> uuid::Uuid {
-    get_test_repos()
-        .await
-        .user
-        .get_id_by_did(did)
-        .await
-        .expect("DB error looking up the user id")
-        .expect("User not found")
+    user_id_of(get_test_repos().await, did).await
 }
 
 #[tokio::test]

crates/tranquil-pds/tests/validation_edge_cases.rs

@@ -1,7 +1,6 @@
 use tranquil_lexicon::is_valid_did;
 use tranquil_pds::api::validation::{
-    HandleValidationError, MAX_DOMAIN_LABEL_LENGTH, MAX_EMAIL_LENGTH, MAX_LOCAL_PART_LENGTH,
-    MAX_SERVICE_HANDLE_LOCAL_PART, is_valid_email, validate_short_handle,
+    HandleValidationError, MAX_SERVICE_HANDLE_LOCAL_PART, validate_short_handle,
 };
 use tranquil_pds::validation::{validate_collection_nsid, validate_password, validate_record_key};
 
@@ -261,83 +260,3 @@ fn test_handle_whitespace_handling() {
         Err(HandleValidationError::ContainsSpaces)
     ));
 }
-
-#[test]
-fn test_email_length_boundaries() {
-    let long_local = format!("{}@example.com", "a".repeat(MAX_LOCAL_PART_LENGTH));
-    assert!(is_valid_email(&long_local));
-
-    let too_long_local = format!("{}@example.com", "a".repeat(MAX_LOCAL_PART_LENGTH + 1));
-    assert!(!is_valid_email(&too_long_local));
-
-    let very_long_email = format!("a@{}.com", "a".repeat(240));
-    if very_long_email.len() <= MAX_EMAIL_LENGTH {
-        assert!(is_valid_email(&very_long_email) || !is_valid_email(&very_long_email));
-    }
-}
-
-#[test]
-fn test_email_local_part_special_chars() {
-    assert!(is_valid_email("user.name@example.com"));
-    assert!(is_valid_email("user+tag@example.com"));
-    assert!(is_valid_email("user!def@example.com"));
-    assert!(is_valid_email("user#abc@example.com"));
-    assert!(is_valid_email("user$def@example.com"));
-    assert!(is_valid_email("user%abc@example.com"));
-    assert!(is_valid_email("user&def@example.com"));
-    assert!(is_valid_email("user'abc@example.com"));
-    assert!(is_valid_email("user*def@example.com"));
-    assert!(is_valid_email("user=abc@example.com"));
-    assert!(is_valid_email("user?def@example.com"));
-    assert!(is_valid_email("user^abc@example.com"));
-    assert!(is_valid_email("user_def@example.com"));
-    assert!(is_valid_email("user`abc@example.com"));
-    assert!(is_valid_email("user{def@example.com"));
-    assert!(is_valid_email("user|abc@example.com"));
-    assert!(is_valid_email("user}def@example.com"));
-    assert!(is_valid_email("user~abc@example.com"));
-    assert!(is_valid_email("user-def@example.com"));
-}
-
-#[test]
-fn test_email_local_part_dots() {
-    assert!(!is_valid_email(".user@example.com"));
-    assert!(!is_valid_email("user.@example.com"));
-    assert!(!is_valid_email("user..name@example.com"));
-    assert!(is_valid_email("user.name@example.com"));
-    assert!(is_valid_email("u.s.e.r@example.com"));
-}
-
-#[test]
-fn test_email_domain_labels() {
-    let long_label = "a".repeat(MAX_DOMAIN_LABEL_LENGTH);
-    let valid_domain = format!("user@{}.com", long_label);
-    assert!(is_valid_email(&valid_domain));
-
-    let too_long_label = "a".repeat(MAX_DOMAIN_LABEL_LENGTH + 1);
-    let invalid_domain = format!("user@{}.com", too_long_label);
-    assert!(!is_valid_email(&invalid_domain));
-}
-
-#[test]
-fn test_email_domain_hyphens() {
-    assert!(!is_valid_email("user@-example.com"));
-    assert!(!is_valid_email("user@example-.com"));
-    assert!(is_valid_email("user@ex-ample.com"));
-    assert!(is_valid_email("user@ex--ample.com"));
-}
-
-#[test]
-fn test_email_domain_must_have_dot() {
-    assert!(!is_valid_email("user@localhost"));
-    assert!(!is_valid_email("user@example"));
-    assert!(is_valid_email("user@a.b"));
-}
-
-#[test]
-fn test_email_invalid_chars() {
-    assert!(!is_valid_email("user name@example.com"));
-    assert!(!is_valid_email("user\t@example.com"));
-    assert!(!is_valid_email("user\n@example.com"));
-    assert!(!is_valid_email("user@exam ple.com"));
-}

crates/tranquil-signal/Cargo.toml

@@ -9,6 +9,7 @@ fjall-store = ["dep:fjall"]
 
 [dependencies]
 presage = { workspace = true }
+tranquil-types = { workspace = true }
 async-trait = { workspace = true }
 chrono = { workspace = true }
 fjall = { version = "3", optional = true }

crates/tranquil-signal/src/client.rs

@@ -14,71 +14,7 @@ use tokio_util::sync::CancellationToken;
 use url::Url;
 
 use crate::store::PgSignalStore;
-
-#[derive(Debug, Clone)]
-pub struct SignalUsername(String);
-
-#[derive(Debug, Clone)]
-pub struct InvalidSignalUsername(String);
-
-impl fmt::Display for InvalidSignalUsername {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "invalid signal username: {}", self.0)
-    }
-}
-
-impl std::error::Error for InvalidSignalUsername {}
-
-impl SignalUsername {
-    pub fn parse(username: &str) -> Result<Self, InvalidSignalUsername> {
-        let reject = || Err(InvalidSignalUsername(username.to_string()));
-
-        let Some((base, discriminator)) = username.rsplit_once('.') else {
-            return reject();
-        };
-
-        if !matches!(base.len(), 3..=32) {
-            return reject();
-        }
-
-        if !base.chars().next().is_some_and(|c| c.is_ascii_alphabetic()) {
-            return reject();
-        }
-
-        if !base.chars().all(|c| c.is_ascii_alphanumeric() || c == '_') {
-            return reject();
-        }
-
-        if !is_valid_discriminator(discriminator) {
-            return reject();
-        }
-
-        Ok(Self(username.to_string()))
-    }
-
-    pub fn as_str(&self) -> &str {
-        &self.0
-    }
-}
-
-fn is_valid_discriminator(s: &str) -> bool {
-    if !s.chars().all(|c| c.is_ascii_digit()) {
-        return false;
-    }
-    if !matches!(s.len(), 2..=20) {
-        return false;
-    }
-    if s.len() > 2 && s.starts_with('0') {
-        return false;
-    }
-    s.parse::<u64>().is_ok_and(|n| n != 0)
-}
-
-impl fmt::Display for SignalUsername {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str(&self.0)
-    }
-}
+use tranquil_types::SignalUsername;
 
 #[derive(Debug, Clone)]
 pub struct DeviceName(String);

crates/tranquil-signal/src/lib.rs

@@ -10,11 +10,12 @@ mod tests;
 mod tests_fjall;
 
 pub use client::{
-    DeviceName, InvalidDeviceName, InvalidSignalUsername, LinkGeneration, LinkResult, MessageBody,
-    MessageTooLong, SignalClient, SignalError, SignalSlot, SignalUsername,
+    DeviceName, InvalidDeviceName, LinkGeneration, LinkResult, MessageBody, MessageTooLong,
+    SignalClient, SignalError, SignalSlot,
 };
 pub use presage;
 pub use store::PgSignalStore;
+pub use tranquil_types::{InvalidSignalUsername, SignalUsername};
 
 #[async_trait::async_trait]
 pub trait SignalStoreProvider: Send + Sync {

crates/tranquil-store/src/metastore/client.rs

@@ -13,16 +13,16 @@ use tranquil_db_traits::{
     ImportBlock, ImportRecord, ImportRepoError, InviteCodeError, InviteCodeInfo, InviteCodeRow,
     InviteCodeSortOrder, InviteCodeUse, MigrationReactivationError, MigrationReactivationInput,
     NotificationHistoryRow, NotificationPrefs, OAuthTokenWithUser, PasswordResetResult,
-    PlcTokenInfo, PruneCount, QueuedComms, ReactivatedAccountInfo, RecoverPasskeyAccountInput,
-    RecoverPasskeyAccountResult, RepoAccountInfo, RepoIdentity, RepoInfo, RepoListItem,
-    RepoWithoutRev, ReservedSigningKey, ReservedSigningKeyFull, ScheduledDeletionAccount,
-    ScopePreference, SequenceNumber, SequencedEvent, StoredBackupCode, StoredPasskey,
-    TokenFamilyId, TotpRecord, TotpRecordState, User2faStatus, UserAuthInfo, UserCommsPrefs,
-    UserConfirmSignup, UserDidWebInfo, UserEmailInfo, UserForDeletion, UserForDidDoc,
-    UserForDidDocBuild, UserForPasskeyRecovery, UserForPasskeySetup, UserForRecovery,
-    UserForVerification, UserIdAndHandle, UserIdAndPasswordHash, UserIdHandleEmail,
-    UserInfoForAuth, UserKeyInfo, UserKeyWithId, UserLegacyLoginPref, UserLoginCheck,
-    UserLoginFull, UserLoginInfo, UserNeedingRecordBlobsBackfill, UserPasswordInfo,
+    PlcTokenInfo, PruneCount, QueuedComms, ReactivatedAccountInfo, Recipient,
+    RecoverPasskeyAccountInput, RecoverPasskeyAccountResult, RepoAccountInfo, RepoIdentity,
+    RepoInfo, RepoListItem, RepoWithoutRev, ReservedSigningKey, ReservedSigningKeyFull,
+    ScheduledDeletionAccount, ScopePreference, SequenceNumber, SequencedEvent, StoredBackupCode,
+    StoredPasskey, TokenFamilyId, TotpRecord, TotpRecordState, User2faStatus, UserAuthInfo,
+    UserCommsPrefs, UserConfirmSignup, UserDidWebInfo, UserEmailInfo, UserForDeletion,
+    UserForDidDoc, UserForDidDocBuild, UserForPasskeyRecovery, UserForPasskeySetup,
+    UserForRecovery, UserForVerification, UserIdAndHandle, UserIdAndPasswordHash,
+    UserIdHandleEmail, UserInfoForAuth, UserKeyInfo, UserKeyWithId, UserLegacyLoginPref,
+    UserLoginCheck, UserLoginFull, UserLoginInfo, UserNeedingRecordBlobsBackfill, UserPasswordInfo,
     UserResendVerification, UserResetCodeInfo, UserRow, UserSessionInfo, UserStatus,
     UserVerificationInfo, UserWithKey, UserWithoutBlocks, ValidatedInviteCode,
     WebauthnChallengeType,
@@ -1793,9 +1793,8 @@ impl<S: StorageIO + 'static> tranquil_db_traits::InfraRepository for MetastoreCl
     async fn enqueue_comms(
         &self,
         user_id: Option<Uuid>,
-        channel: CommsChannel,
+        recipient: &Recipient,
         comms_type: CommsType,
-        recipient: &str,
         subject: Option<&str>,
         body: &str,
         metadata: Option<serde_json::Value>,
@@ -1804,9 +1803,8 @@ impl<S: StorageIO + 'static> tranquil_db_traits::InfraRepository for MetastoreCl
         self.pool
             .send(MetastoreRequest::Infra(InfraRequest::EnqueueComms {
                 user_id,
-                channel,
+                recipient: recipient.clone(),
                 comms_type,
-                recipient: recipient.to_owned(),
                 subject: subject.map(str::to_owned),
                 body: body.to_owned(),
                 metadata,
@@ -3736,12 +3734,16 @@ impl<S: StorageIO + 'static> tranquil_db_traits::UserRepository for MetastoreCli
         recv(rx).await
     }
 
-    async fn admin_update_email(&self, did: &Did, email: &str) -> Result<u64, DbError> {
+    async fn admin_update_email(
+        &self,
+        did: &Did,
+        email: &tranquil_types::EmailAddress,
+    ) -> Result<u64, DbError> {
         let (tx, rx) = oneshot::channel();
         self.pool
             .send(MetastoreRequest::User(UserRequest::AdminUpdateEmail {
                 did: did.clone(),
-                email: email.to_owned(),
+                email: email.clone(),
                 tx,
             }))?;
         recv(rx).await
@@ -3888,14 +3890,14 @@ impl<S: StorageIO + 'static> tranquil_db_traits::UserRepository for MetastoreCli
 
     async fn store_telegram_chat_id(
         &self,
-        telegram_username: &str,
+        telegram_username: &tranquil_types::TelegramUsername,
         chat_id: i64,
         handle: Option<&Handle>,
     ) -> Result<Option<Uuid>, DbError> {
         let (tx, rx) = oneshot::channel();
         self.pool
             .send(MetastoreRequest::User(UserRequest::StoreTelegramChatId {
-                telegram_username: telegram_username.to_owned(),
+                telegram_username: telegram_username.clone(),
                 chat_id,
                 handle: handle.map(|h| h.to_string()),
                 tx,
@@ -3903,16 +3905,6 @@ impl<S: StorageIO + 'static> tranquil_db_traits::UserRepository for MetastoreCli
         recv(rx).await
     }
 
-    async fn get_telegram_chat_id(&self, user_id: Uuid) -> Result<Option<i64>, DbError> {
-        let (tx, rx) = oneshot::channel();
-        self.pool
-            .send(MetastoreRequest::User(UserRequest::GetTelegramChatId {
-                user_id,
-                tx,
-            }))?;
-        recv(rx).await
-    }
-
     async fn set_unverified_discord(
         &self,
         user_id: Uuid,
@@ -3930,15 +3922,15 @@ impl<S: StorageIO + 'static> tranquil_db_traits::UserRepository for MetastoreCli
 
     async fn store_discord_user_id(
         &self,
-        discord_username: &str,
-        discord_id: &str,
+        discord_username: &tranquil_types::DiscordUsername,
+        discord_id: &tranquil_types::DiscordUserId,
         handle: Option<&Handle>,
     ) -> Result<Option<Uuid>, DbError> {
         let (tx, rx) = oneshot::channel();
         self.pool
             .send(MetastoreRequest::User(UserRequest::StoreDiscordUserId {
-                discord_username: discord_username.to_owned(),
-                discord_id: discord_id.to_owned(),
+                discord_username: discord_username.clone(),
+                discord_id: discord_id.clone(),
                 handle: handle.map(|h| h.to_string()),
                 tx,
             }))?;

crates/tranquil-store/src/metastore/handler.rs

@@ -15,7 +15,7 @@ use tranquil_db_traits::{
     InviteCodeError, InviteCodeInfo, InviteCodeRow, InviteCodeSortOrder, InviteCodeUse,
     MigrationReactivationError, MigrationReactivationInput, NotificationHistoryRow,
     NotificationPrefs, OAuthTokenWithUser, PasswordResetResult, PlcTokenInfo, QueuedComms,
-    ReactivatedAccountInfo, RecoverPasskeyAccountInput, RecoverPasskeyAccountResult,
+    ReactivatedAccountInfo, Recipient, RecoverPasskeyAccountInput, RecoverPasskeyAccountResult,
     RefreshSessionResult, RepoIdentity, ReservedSigningKey, ReservedSigningKeyFull,
     ScheduledDeletionAccount, ScopePreference, SequenceNumber, SequencedEvent, SessionId,
     StoredBackupCode, StoredPasskey, TokenFamilyId, TotpRecord, TotpRecordState, User2faStatus,
@@ -1148,7 +1148,7 @@ pub enum UserRequest {
     },
     AdminUpdateEmail {
         did: Did,
-        email: String,
+        email: tranquil_types::EmailAddress,
         tx: Tx<u64>,
     },
     AdminUpdateHandle {
@@ -1202,23 +1202,19 @@ pub enum UserRequest {
         tx: Tx<()>,
     },
     StoreTelegramChatId {
-        telegram_username: String,
+        telegram_username: tranquil_types::TelegramUsername,
         chat_id: i64,
         handle: Option<String>,
         tx: Tx<Option<Uuid>>,
     },
-    GetTelegramChatId {
-        user_id: Uuid,
-        tx: Tx<Option<i64>>,
-    },
     SetUnverifiedDiscord {
         user_id: Uuid,
         discord_username: String,
         tx: Tx<()>,
     },
     StoreDiscordUserId {
-        discord_username: String,
-        discord_id: String,
+        discord_username: tranquil_types::DiscordUsername,
+        discord_id: tranquil_types::DiscordUserId,
         handle: Option<String>,
         tx: Tx<Option<Uuid>>,
     },
@@ -1744,7 +1740,6 @@ impl UserRequest {
             | Self::ClearSignal { user_id, .. }
             | Self::SetUnverifiedSignal { user_id, .. }
             | Self::SetUnverifiedTelegram { user_id, .. }
-            | Self::GetTelegramChatId { user_id, .. }
             | Self::SetUnverifiedDiscord { user_id, .. }
             | Self::VerifyEmailChannel { user_id, .. }
             | Self::VerifyDiscordChannel { user_id, .. }
@@ -1810,9 +1805,8 @@ impl UserRequest {
 pub enum InfraRequest {
     EnqueueComms {
         user_id: Option<Uuid>,
-        channel: CommsChannel,
+        recipient: Recipient,
         comms_type: CommsType,
-        recipient: String,
         subject: Option<String>,
         body: String,
         metadata: Option<serde_json::Value>,
@@ -3870,9 +3864,8 @@ fn dispatch_infra<S: StorageIO>(state: &HandlerState<S>, req: InfraRequest) {
     match req {
         InfraRequest::EnqueueComms {
             user_id,
-            channel,
-            comms_type,
             recipient,
+            comms_type,
             subject,
             body,
             metadata,
@@ -3883,9 +3876,8 @@ fn dispatch_infra<S: StorageIO>(state: &HandlerState<S>, req: InfraRequest) {
                 .infra_ops()
                 .enqueue_comms(
                     user_id,
-                    channel,
-                    comms_type,
                     &recipient,
+                    comms_type,
                     subject.as_deref(),
                     &body,
                     metadata,
@@ -5300,9 +5292,6 @@ fn dispatch_user<S: StorageIO + 'static>(state: &HandlerState<S>, req: UserReque
                     .map_err(metastore_to_db),
             );
         }
-        UserRequest::GetTelegramChatId { user_id, tx } => {
-            let _ = tx.send(user.get_telegram_chat_id(user_id).map_err(metastore_to_db));
-        }
         UserRequest::SetUnverifiedDiscord {
             user_id,
             discord_username,

crates/tranquil-store/src/metastore/infra_ops.rs

@@ -22,9 +22,9 @@ use super::user_hash::UserHashMap;
 use super::users::UserValue;
 
 use tranquil_db_traits::{
-    AdminAccountInfo, CommsChannel, CommsStatus, CommsType, DeletionRequest,
-    DeletionRequestWithToken, InviteCodeError, InviteCodeInfo, InviteCodeRow, InviteCodeSortOrder,
-    InviteCodeState, InviteCodeUse, NotificationHistoryRow, PlcTokenInfo, QueuedComms,
+    AdminAccountInfo, CommsStatus, CommsType, DeletionRequest, DeletionRequestWithToken,
+    InviteCodeError, InviteCodeInfo, InviteCodeRow, InviteCodeSortOrder, InviteCodeState,
+    InviteCodeUse, NotificationHistoryRow, PlcTokenInfo, QueuedComms, Recipient,
     ReservedSigningKey, ReservedSigningKeyFull, ValidatedInviteCode,
 };
 use tranquil_types::{Did, Handle, InviteCode};
@@ -145,13 +145,11 @@ impl InfraOps {
         })
     }
 
-    #[allow(clippy::too_many_arguments)]
     pub fn enqueue_comms(
         &self,
         user_id: Option<Uuid>,
-        channel: CommsChannel,
+        recipient: &Recipient,
         comms_type: CommsType,
-        recipient: &str,
         subject: Option<&str>,
         body: &str,
         metadata: Option<serde_json::Value>,
@@ -162,9 +160,9 @@ impl InfraOps {
         let value = QueuedCommsValue {
             id,
             user_id,
-            channel: channel_to_u8(channel),
+            channel: channel_to_u8(recipient.channel()),
             comms_type: comms_type_to_u8(comms_type),
-            recipient: recipient.to_owned(),
+            recipient: recipient.as_str().to_owned(),
             subject: subject.map(str::to_owned),
             body: body.to_owned(),
             metadata: metadata.map(|v| serde_json::to_vec(&v).unwrap_or_default()),
@@ -184,9 +182,9 @@ impl InfraOps {
         if let Some(uid) = user_id {
             let history_value = NotificationHistoryValue {
                 id,
-                channel: channel_to_u8(channel),
+                channel: channel_to_u8(recipient.channel()),
                 comms_type: comms_type_to_u8(comms_type),
-                recipient: recipient.to_owned(),
+                recipient: recipient.as_str().to_owned(),
                 subject: subject.map(str::to_owned),
                 body: body.to_owned(),
                 status: status_to_u8(CommsStatus::Pending),

crates/tranquil-store/src/metastore/user_ops.rs

@@ -781,7 +781,11 @@ impl UserOps {
         }))
     }
 
-    pub fn admin_update_email(&self, did: &Did, email: &str) -> Result<u64, MetastoreError> {
+    pub fn admin_update_email(
+        &self,
+        did: &Did,
+        email: &tranquil_types::EmailAddress,
+    ) -> Result<u64, MetastoreError> {
         let user_hash = self.resolve_hash(did.as_str());
         let val = match self.load_user(user_hash)? {
             Some(v) => v,
@@ -796,12 +800,12 @@ impl UserOps {
 
         batch.insert(
             &self.users,
-            user_by_email_key(email).as_slice(),
+            user_by_email_key(email.as_str()).as_slice(),
             user_hash.raw().to_be_bytes(),
         );
 
         let mut updated = val;
-        updated.email = Some(email.to_owned());
+        updated.email = Some(email.as_str().to_owned());
 
         batch.insert(
             &self.users,
@@ -1022,11 +1026,11 @@ impl UserOps {
 
     pub fn store_telegram_chat_id(
         &self,
-        telegram_username: &str,
+        telegram_username: &tranquil_types::TelegramUsername,
         chat_id: i64,
         handle: Option<&str>,
     ) -> Result<Option<Uuid>, MetastoreError> {
-        let idx_key = telegram_lookup_key(telegram_username);
+        let idx_key = telegram_lookup_key(telegram_username.as_str());
         let raw = match self
             .users
             .get(idx_key.as_slice())
@@ -1062,11 +1066,6 @@ impl UserOps {
         Ok(Some(uid))
     }
 
-    pub fn get_telegram_chat_id(&self, user_id: Uuid) -> Result<Option<i64>, MetastoreError> {
-        let user_hash = self.resolve_hash_from_uuid(user_id)?;
-        Ok(self.load_user(user_hash)?.and_then(|v| v.telegram_chat_id))
-    }
-
     pub fn set_unverified_discord(
         &self,
         user_id: Uuid,
@@ -1105,11 +1104,11 @@ impl UserOps {
 
     pub fn store_discord_user_id(
         &self,
-        discord_username: &str,
-        discord_id: &str,
+        discord_username: &tranquil_types::DiscordUsername,
+        discord_id: &tranquil_types::DiscordUserId,
         handle: Option<&str>,
     ) -> Result<Option<Uuid>, MetastoreError> {
-        let idx_key = discord_lookup_key(discord_username);
+        let idx_key = discord_lookup_key(discord_username.as_str());
         let raw = match self
             .users
             .get(idx_key.as_slice())
@@ -1124,7 +1123,7 @@ impl UserOps {
                     };
                     let user_hash = UserHash::from_did(&val.did);
                     self.mutate_user(user_hash, |u| {
-                        u.discord_id = Some(discord_id.to_owned());
+                        u.discord_id = Some(discord_id.as_str().to_owned());
                     })?;
                     return Ok(Some(val.id));
                 }
@@ -1140,7 +1139,7 @@ impl UserOps {
         };
         let uid = val.id;
         self.mutate_user(user_hash, |u| {
-            u.discord_id = Some(discord_id.to_owned());
+            u.discord_id = Some(discord_id.as_str().to_owned());
         })?;
         Ok(Some(uid))
     }

crates/tranquil-types/src/lib.rs

@@ -141,6 +141,7 @@ macro_rules! simple_string_newtype_no_sqlx {
     };
 }
 
+// I keep coming back to this. Is this too tricksy? Let me know.
 macro_rules! validated_string_newtype {
     (
         $(#[$meta:meta])*
@@ -948,6 +949,19 @@ impl CommsChannel {
         }
     }
 
+    pub fn display_name(&self) -> &'static str {
+        match self {
+            CommsChannel::Email => "email",
+            CommsChannel::Discord => "Discord",
+            CommsChannel::Telegram => "Telegram",
+            CommsChannel::Signal => "Signal",
+        }
+    }
+
+    pub fn verifies_via_bot(&self) -> bool {
+        matches!(self, CommsChannel::Telegram | CommsChannel::Discord)
+    }
+
     pub fn from_str_opt(s: &str) -> Option<Self> {
         match s {
             "email" => Some(CommsChannel::Email),
@@ -959,6 +973,420 @@ impl CommsChannel {
     }
 }
 
+impl std::str::FromStr for CommsChannel {
+    type Err = InvalidCommsChannel;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        CommsChannel::from_str_opt(s).ok_or(InvalidCommsChannel)
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct InvalidCommsChannel;
+
+impl fmt::Display for InvalidCommsChannel {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("invalid comms channel")
+    }
+}
+
+impl std::error::Error for InvalidCommsChannel {}
+
+fn normalize_signal_username(raw: &str) -> Result<String, ()> {
+    let trimmed = raw.trim();
+    let clean = trimmed.strip_prefix('@').unwrap_or(trimmed).to_lowercase();
+    let shaped = clean.rsplit_once('.').is_some_and(|(base, discriminator)| {
+        matches!(base.len(), 3..=32)
+            && base.starts_with(|c: char| c.is_ascii_alphabetic())
+            && base.chars().all(|c| c.is_ascii_alphanumeric() || c == '_')
+            && is_valid_discriminator(discriminator)
+    });
+    shaped.then_some(clean).ok_or(())
+}
+
+fn is_valid_discriminator(s: &str) -> bool {
+    if !s.chars().all(|c| c.is_ascii_digit()) {
+        return false;
+    }
+    if !matches!(s.len(), 2..=20) {
+        return false;
+    }
+    if s.len() > 2 && s.starts_with('0') {
+        return false;
+    }
+    s.parse::<u64>().is_ok_and(|n| n != 0)
+}
+
+validated_string_newtype! {
+    pub struct SignalUsername;
+    error = InvalidSignalUsername;
+    label = "Signal username. Must be 3-32 characters starting with a letter, then a full-stop, then at least two digits, like oys.01";
+    validator = normalize_signal_username;
+}
+
+fn normalize_telegram_username(raw: &str) -> Result<String, ()> {
+    let trimmed = raw.trim();
+    let clean = trimmed.strip_prefix('@').unwrap_or(trimmed).to_lowercase();
+    let shaped = (5..=32).contains(&clean.len())
+        && clean.chars().all(|c| c.is_ascii_alphanumeric() || c == '_');
+    shaped.then_some(clean).ok_or(())
+}
+
+validated_string_newtype! {
+    pub struct TelegramUsername;
+    error = InvalidTelegramUsername;
+    label = "Telegram username. Must be 5-32 characters of letters, digits, or underscores";
+    validator = normalize_telegram_username;
+}
+
+fn normalize_discord_username(raw: &str) -> Result<String, ()> {
+    let clean = raw.trim().to_lowercase();
+    let shaped = (2..=32).contains(&clean.len())
+        && !clean.contains("..")
+        && clean
+            .chars()
+            .all(|c| c.is_ascii_lowercase() || c.is_ascii_digit() || c == '_' || c == '.');
+    shaped.then_some(clean).ok_or(())
+}
+
+validated_string_newtype! {
+    pub struct DiscordUsername;
+    error = InvalidDiscordUsername;
+    label = "Discord username. Must be 2-32 lowercase letters, digits, underscores, or full-stops";
+    validator = normalize_discord_username;
+}
+
+const MAX_EMAIL_LENGTH: usize = 254;
+const MAX_EMAIL_LOCAL_PART_LENGTH: usize = 64;
+const MAX_EMAIL_DOMAIN_LENGTH: usize = 253;
+const MAX_EMAIL_DOMAIN_LABEL_LENGTH: usize = 63;
+const EMAIL_LOCAL_FUNNY_CHARS: &str = ".!#$%&'*+/=?^_`{|}~-";
+
+validated_string_newtype! {
+    pub struct EmailAddress;
+    error = InvalidEmailAddress;
+    label = "email address";
+    validator = |raw| {
+        let clean = raw.trim().to_ascii_lowercase();
+        is_valid_email(&clean).then_some(clean).ok_or(())
+    };
+}
+
+fn is_valid_email(email: &str) -> bool {
+    email.len() <= MAX_EMAIL_LENGTH
+        && email.rsplit_once('@').is_some_and(|(local, domain)| {
+            valid_email_local_part(local) && valid_email_domain(domain)
+        })
+}
+
+fn valid_email_local_part(local: &str) -> bool {
+    !local.is_empty()
+        && local.len() <= MAX_EMAIL_LOCAL_PART_LENGTH
+        && !local.starts_with('.')
+        && !local.ends_with('.')
+        && !local.contains("..")
+        && local
+            .chars()
+            .all(|c| c.is_ascii_alphanumeric() || EMAIL_LOCAL_FUNNY_CHARS.contains(c))
+}
+
+fn valid_email_domain(domain: &str) -> bool {
+    !domain.is_empty()
+        && domain.len() <= MAX_EMAIL_DOMAIN_LENGTH
+        && domain.contains('.')
+        && domain.split('.').all(|label| {
+            !label.is_empty()
+                && label.len() <= MAX_EMAIL_DOMAIN_LABEL_LENGTH
+                && !label.starts_with('-')
+                && !label.ends_with('-')
+                && label.chars().all(|c| c.is_ascii_alphanumeric() || c == '-')
+        })
+}
+
+fn valid_telegram_chat_id(raw: &str) -> Result<String, ()> {
+    let digits = raw.strip_prefix('-').unwrap_or(raw);
+    let accepted = !digits.is_empty()
+        && digits.bytes().all(|b| b.is_ascii_digit())
+        && raw.len() <= 20
+        && raw.parse::<i64>().is_ok_and(|id| id != 0);
+    accepted.then(|| raw.to_string()).ok_or(())
+}
+
+validated_string_newtype! {
+    pub struct TelegramChatId;
+    error = InvalidTelegramChatId;
+    label = "Telegram chat ID";
+    validator = valid_telegram_chat_id;
+}
+
+// Particularly from having been stored in the DB as a 0, so that the state is shown nicely within our engine.
+impl TelegramChatId {
+    pub fn from_i64(id: i64) -> Option<Self> {
+        (id != 0).then(|| Self(id.to_string()))
+    }
+}
+
+fn valid_discord_user_id(raw: &str) -> Result<String, ()> {
+    raw.parse::<u64>()
+        .is_ok_and(|id| id > 0)
+        .then(|| raw.to_string())
+        .ok_or(())
+}
+
+validated_string_newtype! {
+    pub struct DiscordUserId;
+    error = InvalidDiscordUserId;
+    label = "Discord user ID";
+    validator = valid_discord_user_id;
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum Recipient {
+    Email(EmailAddress),
+    Signal(SignalUsername),
+    Telegram(TelegramChatId),
+    Discord(DiscordUserId),
+}
+
+#[derive(Debug, Clone)]
+pub struct InvalidRecipient {
+    channel: CommsChannel,
+    raw: String,
+}
+
+impl fmt::Display for InvalidRecipient {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "invalid {} recipient: {}", self.channel, self.raw)
+    }
+}
+
+impl std::error::Error for InvalidRecipient {}
+
+impl Recipient {
+    pub fn new(channel: CommsChannel, raw: &str) -> Result<Self, InvalidRecipient> {
+        let parsed = match channel {
+            CommsChannel::Email => EmailAddress::new(raw).ok().map(Self::Email),
+            CommsChannel::Signal => SignalUsername::new(raw).ok().map(Self::Signal),
+            CommsChannel::Telegram => TelegramChatId::new(raw).ok().map(Self::Telegram),
+            CommsChannel::Discord => DiscordUserId::new(raw).ok().map(Self::Discord),
+        };
+        parsed.ok_or(InvalidRecipient {
+            channel,
+            raw: raw.to_string(),
+        })
+    }
+
+    pub fn channel(&self) -> CommsChannel {
+        match self {
+            Self::Email(_) => CommsChannel::Email,
+            Self::Signal(_) => CommsChannel::Signal,
+            Self::Telegram(_) => CommsChannel::Telegram,
+            Self::Discord(_) => CommsChannel::Discord,
+        }
+    }
+
+    pub fn as_str(&self) -> &str {
+        match self {
+            Self::Email(address) => address.as_str(),
+            Self::Signal(username) => username.as_str(),
+            Self::Telegram(chat_id) => chat_id.as_str(),
+            Self::Discord(user_id) => user_id.as_str(),
+        }
+    }
+}
+
+impl fmt::Display for Recipient {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+#[cfg(test)]
+mod recipient_tests {
+    use super::*;
+
+    #[test]
+    fn email_new_normalizes_and_validates() {
+        let address = EmailAddress::new("  User@Example.PET \n").unwrap();
+        assert_eq!(address.as_str(), "user@example.pet");
+        assert!(EmailAddress::new("").is_err());
+        assert!(EmailAddress::new("no-at-sign").is_err());
+        assert!(EmailAddress::new("a@-bad.label.pet").is_err());
+        assert!(EmailAddress::new("dot..dot@jola.dev").is_err());
+        assert!(EmailAddress::new(".user@nel.pet").is_err());
+        assert!(EmailAddress::new("user.@nel.pet").is_err());
+        assert!(EmailAddress::new("u.s.e.r@jola.dev").is_ok());
+        assert!(EmailAddress::new("a b@nel.pet").is_err());
+        assert!(EmailAddress::new("user\t@nel.pet").is_err());
+        assert!(EmailAddress::new("user@exam ple.pet").is_err());
+        assert!(EmailAddress::new("user@localhost").is_err());
+        assert!(EmailAddress::new("user@ex-ample.pet").is_ok());
+        assert!(EmailAddress::new("user@ex--ample.pet").is_ok());
+        assert!(EmailAddress::new("user@example-.pet").is_err());
+        assert!(EmailAddress::new("USER@JOLA.DEV").is_ok());
+    }
+
+    #[test]
+    fn email_accepts_every_local_part_special_char() {
+        for special in [
+            "user.name",
+            "user+tag",
+            "user!def",
+            "user#abc",
+            "user$def",
+            "user%abc",
+            "user&def",
+            "user'abc",
+            "user*def",
+            "user=abc",
+            "user?def",
+            "user^abc",
+            "user_def",
+            "user`abc",
+            "user{def",
+            "user|def",
+            "user}def",
+            "user~def",
+            "user-def",
+        ] {
+            assert!(
+                EmailAddress::new(format!("{special}@jola.dev")).is_ok(),
+                "{special} is an allowed local part character"
+            );
+        }
+    }
+
+    #[test]
+    fn telegram_chat_id_accepts_groups_and_rejects_usernames() {
+        assert_eq!(
+            TelegramChatId::new("-1001234567890").unwrap().as_str(),
+            "-1001234567890"
+        );
+        assert_eq!(TelegramChatId::new("42").unwrap().as_str(), "42");
+        assert_eq!(
+            TelegramChatId::from_i64(-1001234567890).unwrap().as_str(),
+            "-1001234567890"
+        );
+        assert!(TelegramChatId::from_i64(0).is_none());
+        let every_minted_value_parses = [1, -1, -1001234567890, i64::MAX, i64::MIN]
+            .into_iter()
+            .filter_map(TelegramChatId::from_i64)
+            .all(|id| TelegramChatId::new(id.to_string()).is_ok());
+        assert!(every_minted_value_parses);
+        assert!(TelegramChatId::new("oys_01").is_err());
+        assert!(TelegramChatId::new("+42").is_err());
+        assert!(TelegramChatId::new("").is_err());
+        assert!(TelegramChatId::new("9999999999999999999999").is_err());
+        assert!(TelegramChatId::new("0").is_err());
+        assert!(TelegramChatId::new("-0").is_err());
+    }
+
+    #[test]
+    fn email_enforces_length_boundaries() {
+        let domain_189 = format!("{}.{}.{}", "a".repeat(63), "b".repeat(63), "c".repeat(61));
+        let max = format!("{}@{}", "d".repeat(64), domain_189);
+        assert_eq!(max.len(), 254);
+        assert!(EmailAddress::new(&max).is_ok());
+
+        let domain_190 = format!("{}.{}.{}", "a".repeat(63), "b".repeat(63), "c".repeat(62));
+        let over = format!("{}@{}", "d".repeat(64), domain_190);
+        assert_eq!(over.len(), 255);
+        assert!(EmailAddress::new(&over).is_err());
+
+        assert!(EmailAddress::new(format!("{}@nel.pet", "a".repeat(64))).is_ok());
+        assert!(EmailAddress::new(format!("{}@jola.dev", "a".repeat(65))).is_err());
+        assert!(EmailAddress::new(format!("a@{}.pet", "b".repeat(63))).is_ok());
+        assert!(EmailAddress::new(format!("a@{}.pet", "b".repeat(64))).is_err());
+    }
+
+    #[test]
+    fn discord_user_id_requires_positive_snowflake() {
+        assert_eq!(
+            DiscordUserId::new("274656283714826240").unwrap().as_str(),
+            "274656283714826240"
+        );
+        assert!(DiscordUserId::new("0").is_err());
+        assert!(DiscordUserId::new("-1").is_err());
+        assert!(DiscordUserId::new("oys").is_err());
+        assert!(DiscordUserId::new("18446744073709551616").is_err());
+    }
+
+    #[test]
+    fn username_new_normalizes_sigil_and_case() {
+        assert_eq!(
+            TelegramUsername::new("  @Oys_01 ").unwrap().as_str(),
+            "oys_01"
+        );
+        assert_eq!(
+            DiscordUsername::new(" Oys.Cafe ").unwrap().as_str(),
+            "oys.cafe"
+        );
+        assert_eq!(SignalUsername::new("@Oys.01").unwrap().as_str(), "oys.01");
+        assert!(TelegramUsername::new("oys").is_err());
+        assert!(TelegramUsername::new("oys-01").is_err());
+        assert!(TelegramUsername::new("123456789012345678901234567890123").is_err());
+        assert!(DiscordUsername::new("a").is_err());
+        assert!(DiscordUsername::new("user..name").is_err());
+        assert!(DiscordUsername::new("user-name").is_err());
+    }
+
+    #[test]
+    fn signal_discriminators_have_exact_boundaries() {
+        for valid in [
+            "oys.01",
+            "oyster_cafe.99",
+            "user123.42",
+            "lu1.01",
+            "a_very_long_username_here.55",
+            "oys.123",
+            "oys.999999999",
+            "oys.18446744073709551615",
+        ] {
+            assert!(SignalUsername::new(valid).is_ok(), "{valid}");
+        }
+        for invalod in [
+            "",
+            "oys",
+            "oys.1",
+            "oys.001",
+            "abc.00",
+            "oys.0",
+            "oys.999999999999999999999",
+            ".01",
+            "ab.01",
+            "1oys.01",
+            "oys!.01",
+            "oys .01",
+            "oys.01; rm -rf /",
+            "oys.01 && cat /etc/passwd",
+            "oys.01`id`",
+            "oys.01$(whoami)",
+        ] {
+            assert!(SignalUsername::new(invalod).is_err(), "{invalod}");
+        }
+        assert!(SignalUsername::new("a".repeat(33)).is_err());
+        assert!(SignalUsername::new(format!("{}.01", "a".repeat(32))).is_ok());
+    }
+
+    #[test]
+    fn recipient_parse_binds_channel_to_value() {
+        let email = Recipient::new(CommsChannel::Email, "oys@nel.pet").unwrap();
+        assert_eq!(email.channel(), CommsChannel::Email);
+        assert_eq!(email.as_str(), "oys@nel.pet");
+        let signal = Recipient::new(CommsChannel::Signal, "oys.01").unwrap();
+        assert_eq!(signal.channel(), CommsChannel::Signal);
+        let telegram = Recipient::new(CommsChannel::Telegram, "-100").unwrap();
+        assert_eq!(telegram.channel(), CommsChannel::Telegram);
+        let discord = Recipient::new(CommsChannel::Discord, "274656283714826240").unwrap();
+        assert_eq!(discord.channel(), CommsChannel::Discord);
+
+        let mismatch = Recipient::new(CommsChannel::Telegram, "oys_01").unwrap_err();
+        assert_eq!(mismatch.to_string(), "invalid telegram recipient: oys_01");
+        assert!(Recipient::new(CommsChannel::Discord, "oys#0001").is_err());
+        assert!(Recipient::new(CommsChannel::Signal, "oys").is_err());
+    }
+}
+
 impl fmt::Display for CommsChannel {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", self.as_str())