mail: an outbox that cannot clog, and card mails that stay true

Mails the relay refused ten times kept sent_at NULL and stayed in the
50-row window send_pending reads, so fifty of them stopped every later
mail for good. They are now left out of that query and kept only for
mail-status.

A card mail is checked against its card before it is sent and dropped
when the card has been finished, deleted, re-dated or put on a board
that was switched off. Due-card mails and the digest skip spaces whose
board is off, as the agenda already did. The reminder needs a diary
space to exist.

Mails that were sent or given up on are pruned after 90 days. A card's
key is kept while the card exists, because an overdue card is asked
about every day and the key is what stops a second mail.

src/mail/mod.rs

@@ -131,10 +131,14 @@ fn retry_due(attempts: i64, last_attempt_at: Option<i64>, now: i64) -> bool {
 /// Send everything the outbox is holding. Failures are recorded on the row and
 /// retried later; one bad message does not block the ones behind it.
 pub async fn send_pending(db: &SqlitePool, mailer: &Mailer) -> Result<usize> {
+    // A mail the relay refused for good stays in the table for mail-status to
+    // show, and out of this query: counted towards the limit, enough of them
+    // would crowd out every mail queued after them, for ever.
     let rows = sqlx::query(
         "SELECT id, subject, body, attempts, last_attempt_at FROM notifications
-         WHERE sent_at IS NULL ORDER BY created_at LIMIT 50",
+         WHERE sent_at IS NULL AND attempts < ?1 ORDER BY created_at LIMIT 50",
     )
+    .bind(MAX_ATTEMPTS)
     .fetch_all(db)
     .await?;
 
@@ -184,6 +188,31 @@ pub async fn send_pending(db: &SqlitePool, mailer: &Mailer) -> Result<usize> {
     Ok(sent)
 }
 
+/// How long a mail that is done with — sent, or given up on — is kept.
+const KEEP_DAYS: i64 = 90;
+
+/// Forget mails that are done with and can never be asked about again. A key
+/// that names a day, a week or an hour is never asked again once that has
+/// passed; a card's key stays as long as its card does, because an overdue
+/// card is asked about every day it stays overdue.
+pub async fn prune(db: &SqlitePool, now: i64) -> Result<u64> {
+    let removed = sqlx::query(
+        "DELETE FROM notifications
+         WHERE created_at < ?1
+           AND (sent_at IS NOT NULL OR attempts >= ?2)
+           AND (kind <> 'card_due' OR NOT EXISTS (
+               SELECT 1 FROM cards c
+               WHERE c.id = CAST(substr(dedupe_key, 10, instr(substr(dedupe_key, 10), ':') - 1) AS INTEGER)
+           ))",
+    )
+    .bind(now - KEEP_DAYS * 86_400)
+    .bind(MAX_ATTEMPTS)
+    .execute(db)
+    .await?
+    .rows_affected();
+    Ok(removed)
+}
+
 #[cfg(test)]
 mod tests {
     use super::{retry_due, MAX_ATTEMPTS};
@@ -231,4 +260,79 @@ mod tests {
             .expect("counting works");
         assert_eq!(queued, 1);
     }
+
+    async fn outbox() -> sqlx::SqlitePool {
+        let db = sqlx::SqlitePool::connect("sqlite::memory:").await.unwrap();
+        sqlx::migrate!("./migrations").run(&db).await.unwrap();
+        db
+    }
+
+    #[tokio::test]
+    async fn mails_given_up_on_do_not_hold_up_the_rest() {
+        let db = outbox().await;
+        for n in 0..60 {
+            super::enqueue(&db, "reminder", &format!("dead:{n}"), "s", "b").await.unwrap();
+        }
+        sqlx::query("UPDATE notifications SET attempts = ?1, last_attempt_at = 0")
+            .bind(MAX_ATTEMPTS)
+            .execute(&db)
+            .await
+            .unwrap();
+        super::enqueue(&db, "reminder", "reminder:2026-10-20", "s", "b").await.unwrap();
+
+        let next: Vec<String> = sqlx::query_scalar(
+            "SELECT dedupe_key FROM notifications WHERE sent_at IS NULL AND attempts < ?1
+             ORDER BY created_at LIMIT 50",
+        )
+        .bind(MAX_ATTEMPTS)
+        .fetch_all(&db)
+        .await
+        .unwrap();
+        assert_eq!(next, ["reminder:2026-10-20"]);
+    }
+
+    #[tokio::test]
+    async fn old_mails_go_but_a_live_cards_key_stays() {
+        let db = outbox().await;
+        let space: i64 = sqlx::query_scalar(
+            "INSERT INTO nodes (parent_id, kind, name, slug, has_board, created_at, updated_at)
+             VALUES (NULL, 'space', 'job', 'job', 1, 0, 0) RETURNING id",
+        )
+        .fetch_one(&db)
+        .await
+        .unwrap();
+        let list: i64 = sqlx::query_scalar(
+            "INSERT INTO board_lists (space_id, name, position, created_at) VALUES (?1, 'l', 0, 0) RETURNING id",
+        )
+        .bind(space)
+        .fetch_one(&db)
+        .await
+        .unwrap();
+        let card: i64 = sqlx::query_scalar(
+            "INSERT INTO cards (list_id, title, position, created_at, updated_at)
+             VALUES (?1, 'c', 0, 0, 0) RETURNING id",
+        )
+        .bind(list)
+        .fetch_one(&db)
+        .await
+        .unwrap();
+        for key in [
+            "reminder:2026-01-01".to_string(),
+            format!("card_due:{card}:2026-01-01:overdue"),
+            "card_due:999999:2026-01-01:overdue".to_string(),
+        ] {
+            super::enqueue(&db, "x", &key, "s", "b").await.unwrap();
+        }
+        sqlx::query("UPDATE notifications SET sent_at = 1, created_at = 1, kind = CASE WHEN dedupe_key LIKE 'card_due:%' THEN 'card_due' ELSE 'reminder' END")
+            .execute(&db)
+            .await
+            .unwrap();
+
+        assert_eq!(super::prune(&db, crate::now()).await.unwrap(), 2);
+        let left: Vec<String> = sqlx::query_scalar("SELECT dedupe_key FROM notifications")
+            .fetch_all(&db)
+            .await
+            .unwrap();
+        assert_eq!(left, [format!("card_due:{card}:2026-01-01:overdue")]);
+    }
 }

src/notify/mod.rs

@@ -54,7 +54,9 @@ impl Notifier {
             // already in it are the ones that matter most.
             tracing::error!(error = %format!("{e:#}"), "the notification sweep failed");
         }
+        self.drop_stale_cards().await?;
         mail::send_pending(&self.db, mailer).await?;
+        mail::prune(&self.db, crate::now()).await?;
         Ok(())
     }
 
@@ -93,7 +95,11 @@ impl Notifier {
     /// "You have not written today." Asked once the reminder time has passed,
     /// and only if the diary space gained no document that local day.
     async fn sweep_reminder(&self, today: NaiveDate) -> Result<()> {
-        if diary_written(&self.db, self.config.mail.timezone, today).await? {
+        let has_diary = sqlx::query("SELECT 1 FROM nodes WHERE role = 'diary'")
+            .fetch_optional(&self.db)
+            .await?
+            .is_some();
+        if !has_diary || diary_written(&self.db, self.config.mail.timezone, today).await? {
             return Ok(());
         }
 
@@ -118,6 +124,7 @@ impl Notifier {
              JOIN board_lists l ON l.id = c.list_id
              JOIN nodes s ON s.id = l.space_id
              WHERE c.done_at IS NULL AND c.due_at IS NOT NULL AND c.due_at < ?
+               AND s.has_board = 1
              ORDER BY c.due_at",
         )
         .bind(end_of_today)
@@ -188,7 +195,7 @@ impl Notifier {
              FROM cards c
              JOIN board_lists l ON l.id = c.list_id
              JOIN nodes s ON s.id = l.space_id
-             WHERE c.done_at >= ? AND c.done_at < ?
+             WHERE c.done_at >= ? AND c.done_at < ? AND s.has_board = 1
              ORDER BY s.position, c.done_at",
         )
         .bind(start)
@@ -202,6 +209,7 @@ impl Notifier {
              JOIN board_lists l ON l.id = c.list_id
              JOIN nodes s ON s.id = l.space_id
              WHERE c.done_at IS NULL AND c.due_at IS NOT NULL AND c.due_at < ?
+               AND s.has_board = 1
              ORDER BY c.due_at",
         )
         .bind(end)
@@ -330,6 +338,41 @@ impl Notifier {
         }
     }
 
+    /// A card mail waiting to go out is checked against its card first: one
+    /// that has since been finished, deleted, re-dated or taken off a board
+    /// that was switched off is no longer news, and is dropped unsent.
+    async fn drop_stale_cards(&self) -> Result<()> {
+        let tz = self.config.mail.timezone;
+        let waiting = sqlx::query(
+            "SELECT n.id, n.dedupe_key, c.due_at, c.done_at, s.has_board
+             FROM notifications n
+             LEFT JOIN cards c
+               ON c.id = CAST(substr(n.dedupe_key, 10, instr(substr(n.dedupe_key, 10), ':') - 1) AS INTEGER)
+             LEFT JOIN board_lists l ON l.id = c.list_id
+             LEFT JOIN nodes s ON s.id = l.space_id
+             WHERE n.kind = 'card_due' AND n.sent_at IS NULL",
+        )
+        .fetch_all(&self.db)
+        .await?;
+
+        for row in waiting {
+            let key: String = row.get("dedupe_key");
+            let card = CardNow {
+                due_at: row.get("due_at"),
+                done_at: row.get("done_at"),
+                has_board: row.get("has_board"),
+            };
+            if !still_due(tz, &key, &card) {
+                sqlx::query("DELETE FROM notifications WHERE id = ?1")
+                    .bind(row.get::<i64, _>("id"))
+                    .execute(&self.db)
+                    .await?;
+                tracing::info!(key, "dropped a card mail that is no longer due");
+            }
+        }
+        Ok(())
+    }
+
     async fn enqueue(&self, kind: &str, key: &str, subject: &str, body: &str) -> Result<()> {
         if mail::enqueue(&self.db, kind, key, subject, body).await? {
             tracing::info!(kind, key, "queued a notification");
@@ -355,6 +398,22 @@ impl Notifier {
     }
 }
 
+/// A card as it stands now, every field `None` when it has been deleted.
+struct CardNow {
+    due_at: Option<i64>,
+    done_at: Option<i64>,
+    has_board: Option<bool>,
+}
+
+/// Whether a card mail queued under `key` — `card_due:<id>:<day>:<stage>` —
+/// still says something true about its card.
+fn still_due(tz: Tz, key: &str, card: &CardNow) -> bool {
+    let queued_for = key.split(':').nth(2);
+    card.done_at.is_none()
+        && card.has_board == Some(true)
+        && card.due_at.map(|due| local_day(tz, due).to_string()).as_deref() == queued_for
+}
+
 /// Run the notifier for as long as the server lives.
 pub fn spawn(notifier: Arc<Notifier>) {
     if !notifier.enabled() {
@@ -485,6 +544,24 @@ mod tests {
     use chrono::NaiveDate;
     use chrono_tz::Europe::Berlin;
 
+    #[test]
+    fn a_card_mail_is_only_sent_while_it_is_true() {
+        let tz = chrono_tz::UTC;
+        let due = chrono::TimeZone::with_ymd_and_hms(&chrono::Utc, 2026, 10, 20, 12, 0, 0).unwrap().timestamp();
+        let key = "card_due:7:2026-10-20:due";
+        let open = super::CardNow { due_at: Some(due), done_at: None, has_board: Some(true) };
+        assert!(super::still_due(tz, key, &open));
+
+        let finished = super::CardNow { done_at: Some(due), ..open };
+        assert!(!super::still_due(tz, key, &finished));
+        let moved = super::CardNow { due_at: Some(due + 86_400), done_at: None, has_board: Some(true) };
+        assert!(!super::still_due(tz, key, &moved));
+        let board_off = super::CardNow { due_at: Some(due), done_at: None, has_board: Some(false) };
+        assert!(!super::still_due(tz, key, &board_off));
+        let deleted = super::CardNow { due_at: None, done_at: None, has_board: None };
+        assert!(!super::still_due(tz, key, &deleted));
+    }
+
     fn day(y: i32, m: u32, d: u32) -> NaiveDate {
         NaiveDate::from_ymd_opt(y, m, d).expect("a real date")
     }