fix: look a send up soon after its response got lost, also with the server still there

lib/offline/__tests__/outbox.test.ts

@@ -234,6 +234,13 @@ describe('the outbox', () => {
     // Not tried again on its own.
     await flushQueue('acc', cut as unknown as JMAPClient, { notify: vi.fn(), allowed: () => true });
     expect(cut.sendEmail).toHaveBeenCalledTimes(1);
+
+    // With the server still there, nothing else would start the lookup.
+    const entry = (await readQueue('acc')).outbox[0];
+    await store.area('acc', 'outbox.update', { id: entry.id, status: 'waiting' });
+    const retryLater = vi.fn();
+    await flushQueue('acc', cut as unknown as JMAPClient, { notify: vi.fn(), allowed: () => true, retryLater });
+    expect(retryLater).toHaveBeenCalledTimes(1);
   });
 
   it('sends nothing once the organisation forbids offline mode', async () => {

lib/offline/flush.ts

@@ -52,6 +52,8 @@ export interface FlushDeps {
   stricterNow?: (entry: OutboxEntry) => boolean;
   /** A held send went out (an undo window still open). */
   onScheduled?: (entry: OutboxEntry, result: SendEmailResult) => void;
+  /** A send's connection broke though the server may be fine: look it up again soon. */
+  retryLater?: () => void;
 }
 
 /** A send is taken for at most this long before a closed tab's send counts as uncertain. */
@@ -272,6 +274,7 @@ async function flushLocked(account: string, client: JMAPClient, deps: FlushDeps)
         if (isNetworkFailure(error) || (error instanceof Error && error.name === 'SendUnconfirmedError')) {
           // It may have reached the server: looked up before it goes again.
           await updateOutboxEntry(entry, { status: 'uncertain' });
+          deps.retryLater?.();
           return;
         }
         const text = error instanceof Error ? error.message : String(error);

lib/offline/offline-mode.ts

@@ -534,6 +534,8 @@ export function scheduleFlushAll(delayMs = 1_000): void {
 
 /** How long after a failed policy fetch the outbox asks again. */
 const POLICY_RETRY_MS = 60_000;
+/** A lost response with the server still there: nothing else would start the lookup. */
+const LOOKUP_AGAIN_MS = 30_000;
 
 /** A send held by the server for undo, from the outbox: the undo toast as after any send. */
 function offerUndo(entry: OutboxEntry, result: SendEmailResult): void {
@@ -578,6 +580,7 @@ export async function flushAll(): Promise<void> {
       allowed: () => offlineAllowed(account),
       stricterNow,
       onScheduled: offerUndo,
+      retryLater: () => scheduleFlushAll(LOOKUP_AGAIN_MS),
     }).catch(() => {});
   }
   await refreshQueueState();