fix: stop the date and time pickers offering times past the server's hold limit

src/api/__tests__/jmap-client.test.ts

@@ -409,6 +409,17 @@ describe('JMAPClient', () => {
         expect(client.undoSendHold(30)).toBeUndefined();
       });
 
+      it('gives the latest time a send can be held until, for the date pickers', async () => {
+        global.fetch = mockFetch([{ status: 200, json: withSubmission(2_592_000, true) }]) as any;
+        await client.connect('https://mail.example.com', 'user', 'pass');
+        const now = Date.UTC(2026, 8, 24, 12, 0, 0);
+        expect(client.latestHoldDate(undefined, now)?.toISOString()).toBe('2026-10-01T12:00:00.000Z');
+
+        global.fetch = mockFetch([{ status: 200, json: MOCK_SESSION }]) as any;
+        await client.connect('https://mail.example.com', 'user', 'pass');
+        expect(client.latestHoldDate(undefined, now)).toBeUndefined();
+      });
+
       it('parses only hold-limit rejections', () => {
         expect(parseHoldLimit('Server rejected MAIL-FROM: 501 5.5.4 Requested hold time exceeds maximum of 604800 seconds.')).toBe(604_800);
         expect(parseHoldLimit('Server rejected MAIL-FROM: 550 nope')).toBeNull();

src/api/jmap-client.ts

@@ -1087,6 +1087,15 @@ export class JMAPClient {
     return max;
   }
 
+  /**
+   * The latest time a send from `accountId` can be held until, or undefined
+   * when it can't be held. Caps the "Pick date & time" pickers.
+   */
+  latestHoldDate(accountId?: string, now = Date.now()): Date | undefined {
+    if (!this.hasDelayedSend(accountId)) return undefined;
+    return new Date(now + this.getMaxDelayedSend(accountId) * 1000);
+  }
+
   /**
    * Remember the hold limit a rejected submission named, so the pickers only
    * offer times the server accepts for the rest of the session.

src/screens/ComposeScreen.tsx

@@ -1895,7 +1895,9 @@ export default function ComposeScreen({ route, navigation }: Props) {
   }, [t, scheduleSheetOpen]);
 
   const startCustomPicker = () => {
-    customDraftRef.current = new Date(Date.now() + 3600 * 1000);
+    // An hour ahead, or the latest time the server can hold it if sooner.
+    const latest = jmapClient.latestHoldDate()?.getTime() ?? Infinity;
+    customDraftRef.current = new Date(Math.min(Date.now() + 3600 * 1000, latest));
     setScheduleSheetOpen(false);
     setCustomStage(Platform.OS === 'ios' ? 'datetime' : 'date');
   };
@@ -2516,6 +2518,7 @@ export default function ComposeScreen({ route, navigation }: Props) {
                 mode="datetime"
                 display="spinner"
                 minimumDate={new Date()}
+                maximumDate={jmapClient.latestHoldDate()}
                 onChange={onCustomPickerChange}
               />
               <View style={styles.modalActions}>
@@ -2542,6 +2545,7 @@ export default function ComposeScreen({ route, navigation }: Props) {
           mode={customStage === 'time' ? 'time' : 'date'}
           display="default"
           minimumDate={customStage === 'date' ? new Date() : undefined}
+          maximumDate={customStage === 'date' ? jmapClient.latestHoldDate() : undefined}
           onChange={onCustomPickerChange}
         />
       )}

src/screens/ScheduledScreen.tsx

@@ -201,7 +201,9 @@ export default function ScheduledScreen({ navigation }: Props) {
   }, [t, rescheduleFor]);
 
   const startCustomPicker = () => {
-    customDraftRef.current = new Date(Date.now() + 3600 * 1000);
+    // An hour ahead, or the latest time the server can hold it if sooner.
+    const latest = jmapClient.latestHoldDate(rescheduleFor?.accountId)?.getTime() ?? Infinity;
+    customDraftRef.current = new Date(Math.min(Date.now() + 3600 * 1000, latest));
     setCustomStage(Platform.OS === 'ios' ? 'datetime' : 'date');
   };
 
@@ -375,6 +377,7 @@ export default function ScheduledScreen({ navigation }: Props) {
                 mode="datetime"
                 display="spinner"
                 minimumDate={new Date()}
+                maximumDate={jmapClient.latestHoldDate(rescheduleFor?.accountId)}
                 onChange={onCustomPickerChange}
               />
               <View style={styles.cardActions}>
@@ -396,6 +399,7 @@ export default function ScheduledScreen({ navigation }: Props) {
           mode={customStage === 'time' ? 'time' : 'date'}
           display="default"
           minimumDate={customStage === 'date' ? new Date() : undefined}
+          maximumDate={customStage === 'date' ? jmapClient.latestHoldDate(rescheduleFor?.accountId) : undefined}
           onChange={onCustomPickerChange}
         />
       )}