diff --git a/crates/flectar-mail-core/src/db/migrations.rs b/crates/flectar-mail-core/src/db/migrations.rs
index 2822b056..5c9b1e13 100644
--- a/crates/flectar-mail-core/src/db/migrations.rs
+++ b/crates/flectar-mail-core/src/db/migrations.rs
@@ -48,6 +48,7 @@ const MIGRATIONS: &[Migration] = &[
     Migration::Plain(include_str!("migrations/029_mail_transfers.sql")),
     Migration::Plain(include_str!("migrations/030_folder_server_only_unseen.sql")),
     Migration::Plain(include_str!("migrations/031_notification_tracking.sql")),
+    Migration::Plain(include_str!("migrations/032_account_caught_up_at.sql")),
 ];
 pub const LATEST_VERSION: i64 = MIGRATIONS.len() as i64;
 
diff --git a/crates/flectar-mail-core/src/db/migrations/032_account_caught_up_at.sql b/crates/flectar-mail-core/src/db/migrations/032_account_caught_up_at.sql
new file mode 100644
index 00000000..0a85efc3
--- /dev/null
+++ b/crates/flectar-mail-core/src/db/migrations/032_account_caught_up_at.sql
@@ -0,0 +1,5 @@
+-- When the account's last complete sync started: everything its server had
+-- received by then is stored here. Mail that arrives after it, while no copy
+-- of the app is following the account, is what a check in the background
+-- tells the user about.
+ALTER TABLE accounts ADD COLUMN caught_up_at INTEGER;
diff --git a/crates/flectar-mail-core/src/db/repo/accounts.rs b/crates/flectar-mail-core/src/db/repo/accounts.rs
index 45a3ef6a..8afb22cd 100644
--- a/crates/flectar-mail-core/src/db/repo/accounts.rs
+++ b/crates/flectar-mail-core/src/db/repo/accounts.rs
@@ -555,6 +555,16 @@ pub fn update_sync_state_with_error(
     )? != 0)
 }
 
+/// Note that a sync of the account that started at `started` stored all the
+/// mail its Inbox had by then.
+pub fn set_caught_up(conn: &Connection, id: i64, started: i64) -> Result<()> {
+    conn.execute(
+        "UPDATE accounts SET caught_up_at = ?2 WHERE id = ?1",
+        params![id, started],
+    )?;
+    Ok(())
+}
+
 /// Move one account before or after another and compact the persisted order.
 /// A complete rewrite keeps ordering deterministic after any number of moves
 /// and avoids fragile fractional positions.
diff --git a/crates/flectar-mail-core/src/jmap/sync.rs b/crates/flectar-mail-core/src/jmap/sync.rs
index b3782803..ecb95a7b 100644
--- a/crates/flectar-mail-core/src/jmap/sync.rs
+++ b/crates/flectar-mail-core/src/jmap/sync.rs
@@ -8,7 +8,8 @@ use crate::events::CoreEvent;
 use crate::jmap::client::{self, ConnectedClient};
 use crate::models::{AccountConfig, Address, MailProtocol, SenderDeliveryStatus, now_ms, roles};
 use crate::sync::engine::{
-    PriorityFetchCmd, SyncCmd, SyncCtx, configured_sync_interval, set_state, set_state_error,
+    PriorityFetchCmd, SyncCmd, SyncCtx, caught_up, configured_sync_interval, set_state,
+    set_state_error,
 };
 use futures::{FutureExt, Stream, StreamExt};
 use jmap_client::core::error::MethodErrorType;
@@ -122,9 +123,11 @@ async fn actor(
                     ),
                 }
             }
+            let started = now_ms();
             set_state(&ctx, config.id, "syncing").await;
             sync_mailboxes(&ctx, config.id, &connected).await?;
             sync_emails(&ctx, &config, &connected, live_since).await?;
+            caught_up(&ctx, config.id, started).await;
             execute_actions(&ctx, &config, &connected).await?;
             // The counts only explain the badges, so they never fail a sync.
             if let Err(error) = sync_mailbox_counts(&ctx, config.id, &connected).await {
diff --git a/crates/flectar-mail-core/src/sync/engine.rs b/crates/flectar-mail-core/src/sync/engine.rs
index 8f80044d..aa5d107c 100644
--- a/crates/flectar-mail-core/src/sync/engine.rs
+++ b/crates/flectar-mail-core/src/sync/engine.rs
@@ -1280,6 +1280,20 @@ pub(crate) async fn set_state_error(ctx: &SyncCtx, account_id: i64, state: &str,
     set_state_inner(ctx, account_id, state, Some(error)).await;
 }
 
+/// Note that a sync of the account that started at `started` stored all the
+/// mail its Inbox had by then. A check in the background tells of what
+/// arrives after it while the app isn't running (see
+/// `Core::announce_missed`).
+pub(crate) async fn caught_up(ctx: &SyncCtx, account_id: i64, started: i64) {
+    let noted = ctx
+        .db
+        .write(move |conn| repo::accounts::set_caught_up(conn, account_id, started))
+        .await;
+    if let Err(error) = noted {
+        tracing::warn!(account_id, %error, "could not note how far a sync caught up");
+    }
+}
+
 async fn set_state_inner(ctx: &SyncCtx, account_id: i64, state: &str, error: Option<&str>) {
     let st = state.to_string();
     let error = error.map(str::to_owned);
@@ -1469,6 +1483,7 @@ async fn run_cycle(
         inbox_pushed,
     } = mode;
     let account_id = config.id;
+    let started = now_ms();
 
     // The folder list: first thing, then once it is FOLDER_LIST_INTERVAL old.
     let listed_now = !immediate_follow_up && listing.due(tokio::time::Instant::now());
@@ -1545,6 +1560,9 @@ async fn run_cycle(
             inbox_baseline,
         )
         .await?;
+        if !inbox_forward_remaining {
+            caught_up(ctx, account_id, started).await;
+        }
     }
 
     // A manual Sync Now resolves at the foreground Inbox boundary. Finish any
diff --git a/crates/flectar-mail-core/src/sync/gmail.rs b/crates/flectar-mail-core/src/sync/gmail.rs
index bf33a63a..bc965efd 100644
--- a/crates/flectar-mail-core/src/sync/gmail.rs
+++ b/crates/flectar-mail-core/src/sync/gmail.rs
@@ -7,8 +7,8 @@
 //! pending-action queue remain provider-neutral and fully offline-first.
 
 use super::engine::{
-    PriorityFetchCmd, SyncCmd, SyncCtx, configured_sync_interval, emit_sync_status, set_state,
-    set_state_error,
+    PriorityFetchCmd, SyncCmd, SyncCtx, caught_up, configured_sync_interval, emit_sync_status,
+    set_state, set_state_error,
 };
 use crate::db::repo::{self, messages::NewMessage};
 use crate::error::{CoreError, Result};
@@ -2556,6 +2556,7 @@ async fn sync_once(
     live_since: i64,
 ) -> Result<bool> {
     let account_id = config.id;
+    let started = now_ms();
     let mut state = ctx
         .db
         .read(move |conn| repo::gmail::state(conn, account_id))
@@ -2764,6 +2765,10 @@ async fn sync_once(
     if page.next_page_token.is_none() && !page.affected_threads.is_empty() {
         sync_draft_map(ctx, config, api).await?;
     }
+    if page.next_page_token.is_none() {
+        // The history ran out: everything up to this pass is stored.
+        caught_up(ctx, account_id, started).await;
+    }
     Ok(true)
 }
 
diff --git a/crates/flectar-mail-core/src/sync/pop3.rs b/crates/flectar-mail-core/src/sync/pop3.rs
index 5bac295e..5d75dec7 100644
--- a/crates/flectar-mail-core/src/sync/pop3.rs
+++ b/crates/flectar-mail-core/src/sync/pop3.rs
@@ -10,8 +10,8 @@
 //! was.
 
 use super::engine::{
-    PriorityFetchCmd, RestoreRequest, SyncCmd, SyncCtx, configured_sync_interval, set_state,
-    set_state_error,
+    PriorityFetchCmd, RestoreRequest, SyncCmd, SyncCtx, caught_up, configured_sync_interval,
+    set_state, set_state_error,
 };
 use super::ingest::{self, Delivery, Importer};
 use crate::accounts::credentials::{self, Slot};
@@ -75,6 +75,7 @@ pub(crate) async fn run(ctx: SyncCtx, mut config: AccountConfig, mut inputs: Inp
             tracing::warn!(account_id, %error, "completing local POP3 actions failed");
         }
         if next_sync.is_some_and(|at| at <= Instant::now()) {
+            let started = now_ms();
             next_sync = match sync(&ctx, &config, &mut catch_up).await {
                 Ok(synced) => {
                     backoff = Duration::from_secs(1);
@@ -83,6 +84,7 @@ pub(crate) async fn run(ctx: SyncCtx, mut config: AccountConfig, mut inputs: Inp
                     ctx.bus.emit(CoreEvent::NetworkState { online: true });
                     let next = match synced {
                         Synced::Complete => {
+                            caught_up(&ctx, account_id, started).await;
                             finish(&mut waiters, Ok(()));
                             Instant::now() + configured_sync_interval(&ctx.db).await
                         }