I have been working on raven, an opensource ESMTP toolkit for Go from the past couple of months.

I started this for a commercial service we offer which I will not promote here. I thought it would be a good gesture to keep the core transport library for the SMTP server and client implementations opensource. It has subpackages for modern mail transport and auth protocols such as DKIM, SPF, DMARC, ARC etc. The core transport library also supports a variety of extensions:

PIPELINING, SIZE, 8BITMIME, SMTPUTF8

STARTTLS, AUTH, ENHANCEDSTATUSCODES

CHUNKING / BDAT, BINARYMIME

DSN, REQUIRETLS, DELIVERBY

It supports streaming MIME traversal for validation, IDNA, etc.

One cool feature I would like to highlight is the full RFC 5321 addr-spec parser.…