When flutter_secure_storage's platform channel is unavailable (e.g. on certain Android devices), getPassword() throws MissingPluginException. Previously this was not recognised as a permanent error, so the IMAP and JMAP sync loops retried indefinitely with exponential back-off, filling the sync log with repeated failures (as shown in the screenshot). Treat MissingPluginException as a permanent error in both _AccountSync and _JmapAccountSync so the loop stops immediately instead of retrying. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>