Sending was synchronous and failed outright if the network or server hiccupped.
Compose now enqueues to an outbox and a worker delivers in the background.
- New `outbox` Room table (entity + DAO + MIGRATION_4_5, DB v5) holds queued mail.
- MailRepository.sendMessage inserts into the outbox and triggers SendScheduler instead
of sending inline, so compose returns immediately.
- SendWorker (@HiltWorker) drains the outbox over SMTP, deleting each row on success and
returning Result.retry() on failure so WorkManager reattempts with backoff (under a
network constraint); a removed account's queued mail is dropped.
- assemble/test/lint green; verified on the Android 17 emulator — the v4->v5 migration
preserved existing mail, and a composed message was queued, sent by the worker over
SMTP, and round-tripped back into the inbox.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
JMR-devandClaude Opus 4.8
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