There are various email synchronization programs like offlineimap or mbsync, which have some inherent limitations:

  • mbsync does not support IMAP IDLE
  • offlineimap does not yet support Python 3, proper IDLE and threading support would need a complete rewrite


  • support only IMAP, no POP3
  • IMAP IDLE support is a must, especially:
    • reconnection of dropped IDLE connections
    • support IDLE for all IMAP folders
  • be able to synchronize IMAP <-> Maildir at first, IMAP <-> IMAP would be nice to have
  • bullet-proof cryptography, especially with respect to certificate validation and resistance to downgrade attacks (preferably make the TLS version configurable)
  • use inotify API to support immediate synchronization back to the server if a message changes locally
  • as simple configuration as possible with good defaults

nice to have:

  • incorporate an API for external tagging tools like notmuch to synchronize tags if the remote supports it
  • GMail support


Preferably in Rust, using the imap crate as the core.


Try to create a MVP, especially flesh out proper testing and learn enough about the problem.


  • cyphar
    7 months ago by cyphar | Reply

    Just one word of warning (I ran into this last time I tried to write an IMAP client in Rust) -- the IMAP crates all appear to be either slightly or completely broken. There are several but they're all forks of one another and the "best looking" one requires tokio.

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