Multi-user email archive: IMAP/POP3/Gmail → users/{uuid}/{domain}/{local}/{folder}/. Optional S3 (MinIO) for blobs. OAuth2 + bcrypt, UUIDv7, DuckDB+Parquet search.
Critical: NEVER delete or mark emails read on server. Sync is read-only.
Docs: CONTRIBUTING.md — architecture, API, coding standards, testing. TODO.md — roadmap. README.md — config, env vars.