fix: say that a send failed because the device is offline and the message is still there

src/components/email/QuickReplyBox.tsx

@@ -15,7 +15,7 @@ import { sendEmail, patchKeywordsForEmails, SendUnconfirmedError } from '../../a
 import { jmapClient } from '../../api/jmap-client';
 import { pruneEmailSubmissions } from '../../api/submissions';
 import { buildReplyRecipients } from '../../lib/reply-recipients';
-import { partlyRefusedWarning, sendFailureMessage } from '../../lib/send-failure-message';
+import { composerSendFailureMessage, partlyRefusedWarning } from '../../lib/send-failure-message';
 import { buildReplySubject } from '../../lib/subject-prefix';
 import { computeReplyThreadingHeaders } from '../../lib/email-threading';
 import { resolveReplyIdentity } from '../../lib/reply-identity';
@@ -255,7 +255,7 @@ export function QuickReplyBox({ email, jmapAccountId, onMoreOptions, onSent, onF
         );
         return;
       }
-      Alert.alert(t('email_composer.send_failed', 'Failed to send'), sendFailureMessage(err, t));
+      Alert.alert(t('email_composer.send_failed', 'Failed to send'), composerSendFailureMessage(err, t));
     } finally {
       setSending(false);
     }

src/lib/__tests__/send-failure-message.test.ts

@@ -1,10 +1,15 @@
 import { describe, it, expect } from 'vitest';
-import { RequestTimeoutError } from '../../api/jmap-client';
+import fs from 'node:fs';
+import path from 'node:path';
+import { NetworkError, RequestTimeoutError } from '../../api/jmap-client';
+import { useNetworkStore } from '../../stores/network-store';
 import {
   JMAPMethodError, NoLongerScheduledError, RecipientsRefusedError, ScheduleTooLateError, SubmissionQuotaError,
   formatRefusedRecipients,
 } from '../../api/jmap-result';
-import { partlyRefusedWarning, rescheduleFailureNotice, sendFailureMessage } from '../send-failure-message';
+import {
+  composerSendFailureMessage, partlyRefusedWarning, rescheduleFailureNotice, sendFailureMessage,
+} from '../send-failure-message';
 
 // The English fallback stands in for the catalog.
 const t = (key: string, fallback?: string, params?: Record<string, unknown>) =>
@@ -97,3 +102,34 @@ describe('recipients the server refused', () => {
     });
   });
 });
+
+describe('composerSendFailureMessage (offline)', () => {
+  const OFFLINE = /You seem to be offline\. The message is still here/;
+
+  it('says offline instead of the transport error', () => {
+    expect(composerSendFailureMessage(new NetworkError('Network request failed'), t)).toMatch(OFFLINE);
+    expect(composerSendFailureMessage(new TypeError('Network request failed'), t)).toMatch(OFFLINE);
+  });
+
+  it('says offline when the device reports no connection', () => {
+    useNetworkStore.setState({ online: false });
+    try {
+      expect(composerSendFailureMessage(new Error('boom'), t)).toMatch(OFFLINE);
+    } finally {
+      useNetworkStore.setState({ online: true });
+    }
+  });
+
+  it("keeps the server's words and the timeout advice when online", () => {
+    expect(composerSendFailureMessage(new Error('Relay denied'), t)).toBe('Relay denied');
+    expect(composerSendFailureMessage(new RequestTimeoutError(30_000), t)).toMatch(/Check your Sent folder/);
+  });
+
+  it('is what the composer and quick reply show', () => {
+    for (const rel of ['../../screens/ComposeScreen.tsx', '../../components/email/QuickReplyBox.tsx']) {
+      const source = fs.readFileSync(path.resolve(__dirname, rel), 'utf8');
+      expect(source).toMatch(/Alert\.alert\(t\('email_composer\.send_failed', '[^']+'\), composerSendFailureMessage\((e|err), t\)\);/);
+      expect(source).not.toMatch(/[^r]sendFailureMessage\(/);
+    }
+  });
+});

src/lib/send-failure-message.ts

@@ -1,4 +1,5 @@
-import { RequestTimeoutError } from '../api/jmap-client';
+import { NetworkError, RequestTimeoutError } from '../api/jmap-client';
+import { useNetworkStore } from '../stores/network-store';
 import {
   NoLongerScheduledError, RecipientsRefusedError, ScheduleTooLateError, SubmissionQuotaError, formatRefusedRecipients,
   type RefusedRecipient,
@@ -62,6 +63,27 @@ export function sendFailureMessage(error: unknown, t: Translate): string {
     : t('notifications.error_sending', 'Failed to send email');
 }
 
+/**
+ * sendFailureMessage for a message the user is writing (composer, quick
+ * reply): a send that never reached the server because the device is
+ * offline says so, and that the text is still there, instead of "Network
+ * request failed" (webmail email-composer.tsx send_offline). The server is
+ * unreachable when the transport failed (the client's NetworkError, or a
+ * bare fetch TypeError) or the device reports no connection.
+ */
+export function composerSendFailureMessage(error: unknown, t: Translate): string {
+  const offline = error instanceof NetworkError
+    || error instanceof TypeError
+    || !useNetworkStore.getState().online;
+  if (offline && !(error instanceof RequestTimeoutError)) {
+    return t(
+      'email_composer.send_offline',
+      'You seem to be offline. The message is still here, send it again once you are back online.',
+    );
+  }
+  return sendFailureMessage(error, t);
+}
+
 /**
  * The title and message for a "Send now" or reschedule that failed: most
  * failures get `failTitle` and sendFailureMessage (webmail

src/screens/ComposeScreen.tsx

@@ -48,7 +48,7 @@ import {
 } from '../api/email';
 import { jmapClient, RequestTimeoutError, ScheduleTooLateError } from '../api/jmap-client';
 import { pruneEmailSubmissions } from '../api/submissions';
-import { partlyRefusedWarning, sendFailureMessage } from '../lib/send-failure-message';
+import { composerSendFailureMessage, partlyRefusedWarning } from '../lib/send-failure-message';
 import { buildReplyRecipients, type ReplySource } from '../lib/reply-recipients';
 import { buildReplySubject, buildForwardSubject } from '../lib/subject-prefix';
 import { computeReplyThreadingHeaders, generateMessageId, stripMessageIdBrackets } from '../lib/email-threading';
@@ -2559,7 +2559,7 @@ export default function ComposeScreen({ route, navigation }: Props) {
         );
         return;
       }
-      Alert.alert(t('email_composer.send_failed', 'Send failed'), sendFailureMessage(e, t));
+      Alert.alert(t('email_composer.send_failed', 'Send failed'), composerSendFailureMessage(e, t));
     } finally {
       setSending(false);
     }