Samotop

SMTP Relay Server (MTA) library and a sample simple server implemented in Rust with focus on spam elimination and privacy. The motivation is to revive e-mail infrastructure and architecture, address current problems and allow new systems to integrate SMTP. It's called SaMoToP, which could be a nice Czech word.

Usage

Library

See the docs on docs.rs.

Executable

run samotop --help for command-line reference.

Status

We've got a decent SMTP command parser written as a PEG grammar. The model is tightly nit from the RFCs. An async-std based server will hear your SMTP commands, drive the SMTP state machine and correct you if you step aside. Once a mail session is ready, the mail data are currently dumped to the console. After that, you can do it again. See the crate documentation for API status. The samotop crate is published on crates.io.

The executable is not very useful yet except for debugging SMTP itself until common MDA/MTA features are implemented.

Done

• Parse SMTP commands and write responses according to RFCs
• SMTP state machine - helo, mail, rcpt*, data, rset, quit - must be in correct order according to RFCs
• DATA are handled and terminated correctly (escape dot, final dot).
• Simple SMTP MTA, logging smtp session to standard output but able to receive mail from common relays
• Privacy: TLS/STARTTLS supported using rustls
• async/await with async-std backing

To do

• Antispam: Strict SMTP
• Antispam: whitelist and blacklist
• Antispam: greylisting
• Antispam: white/black/grey list with UI - user decides new contact handling
• Antispam: is it encrypted?
• Antispam: reverse lookup
• Antispam: DANE (DNSSEC) with UI - user verifies signatures
• Antispam: SPF
• Processing: Relay mail to another MTA
• Processing: Store mail in Maildir (MDA)
• MDA: User mailbox - mailbox for specific address or alias
• MDA: Domain mailbox - mailbox for unclaimed addresses
• MDA: Smart mailbox - multiple mailbox addresses by convention
• Privacy: Refuse unencrypted session
• Privacy: Encryption at rests, encrypt e-mails, only the recipient will be able to decrypt
• Privacy: Leave no trace, no logs, obfuscated file dates...

Company

In Rust world I have so far found mostly SMTP clients.

• lettre is an SMTP client, it seems to be alive and well!
• segimap by uiri, that's actually an IMAP server.
• rust-smtp by mneumann, last commit 2014, parser coded manually, looks unfinished and abandoned.
• rust-smtp fork of the above with progress by synlestidae in 2016
• ferric-mail by wraithan, looks abandoned since 2014.