Time flies and 0.12.0 preview release is out:
- New way of handling commands - command pattern
- NOM based parser through rustyknife - an alternative to default PEG based parser
- S/MIME encryption of e-mails at rest
- Abuse protection - command timeout
- Merged samotop-model into samotop-core
- Finished crate cleanup and modularization
- viaspf upgrade to 0.3
Well, you may wonder, what can you do with this?
Server binary / docker image
The published server itself is pretty basic. I want it to be a stable show of the server, so it doesn't expose all the latest improvements. It simply stores all incoming mail in a single flat maildir. It will check SPF, talks STARTTLS and will drop connections for lazy, buggy clients on timeout... I went on a journey of discovery here, trying to figure out if single binary docker images from scratch were possible with Rust, and voila - they are!
Samotop library
Dipping into the code a bit, you can achieve a lot more. Consider the example of storing all incoming messages in maildir encrypted with S/MIME so no-one but you can read it once stored... S/MIME is another major addition in this release. Since Samotop can also listen to LMTP, I imagine someone could hook this up with postfix and encrypt e-mails at rest.
async fn main_fut() -> Result<()> {
let setup = Setup::from_args();
let ports = setup.get_service_ports();
let mail_service = Builder::default()
.using(Name::new(setup.get_my_name()))
.using(Accounts::new(setup.absolute_path("accounts")))
.using(SMimeMail::new(
setup.get_id_file_path(),
setup.get_cert_file_path(),
))
.using(Dir::new(setup.get_mail_dir())?)
.using(samotop::mail::spf::provide_viaspf())
.using(SmtpParser::default())
.using(RustlsProvider::from(TlsAcceptor::from(
setup.get_tls_config().await?,
)));
let smtp_service = SmtpService::new(Arc::new(mail_service));
info!("I am {}", setup.get_my_name());
TcpServer::on_all(ports).serve(smtp_service).await
}
Process your mail with a simple IO write implementation
You can implement your own mail dispatch and deal with the message yourself. The traits for that:
pub trait MailDispatch: fmt::Debug {
fn send_mail<'a, 's, 'f>(
&'a self,
session: &'s SessionInfo,
transaction: Transaction,
) -> S2Fut<'f, DispatchResult>
where
'a: 'f,
's: 'f;
}
The task is to put an AsyncWrite sink into the Transaction struct. See the debug mail service for bare basics example.
Forward the mail to some other service
It is also fairly straightforward to forward the mail immediately (no queueing implemented yet) to another service. TCP and Unix socket transports can be used with LMTP. See the examples. Here I pass the mails to dovecot over unix socket mapping recipients to an account per domain:
async fn main_fut() -> Result<()> {
let rcpt_map = Mapper::new(vec![
(Regex::new(".*@(.*)")?, "$1@localhost".to_owned()), // use domain as a user name (all domain basket) anyone@example.org => example.org@localhost
(Regex::new("[^@a-zA-Z0-9]+")?, "-".to_owned()), // sanitize the user name example.org@localhost => example-org@localhost
]);
use samotop::io::client::UnixConnector;
let lmtp_connector: UnixConnector<NoTls> = UnixConnector::default();
let mail_service = Builder::default()
.using(LmtpDispatch::new("/var/run/dovecot/lmtp".to_owned(), lmtp_connector)?.reuse(0))
.using(rcpt_map)
.using(SmtpParser::default());
let smtp_service = SmtpService::new(Arc::new(mail_service));
TcpServer::on("localhost:2525").serve(smtp_service).await
}
And while the Connector is not implemented yet, you could likewise start and use a child process that speaks LMTP on stdio.
What's next?
My vision is that we the people are in charge of our data and communication. Not just as implied by GDPR and similar big talk, but physically, factually. Powerful business players worked hard to centralize mail services, chats and social networks and gave that to governments, leaked it to unauthorized parties... It's not all lost. E-mail is still ubiquitous and can be leveraged for a seamless opt out.
The bigger mission is to
- deliver an SMTP experience, that is easy to provision, subscribe and use by non-technical people with utter focus on privacy and abuse prevention.
- enable instant interaction, like or better than chat experience with pending contacts, networking features, integration to open social networks and more.
- explore new ways of working with mail - step away from the tried and tested inbox concept and explore AI, visualization, information discovery.
- explore the options of improving e-mail infrastructure - specifically address the stuffy security and privacy concerns
I'd like to do to e-mail servers what delta.chat does to e-mail clients 
The Immediate mission is to make a useful contribution, something people can use to solve their problems, something that enchants the Rust community to build a samotop user base to inspire, give feedback and contribute. If you are using samotop, I do want to hear from you and about your use cases.
