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.
We've got a decent SMTP command parser written as a PEG grammar. The model is tightly nit from the RFCs. A tokio 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 streamed 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.
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.