Streaming MIME parsing + SMTP server performance

[xeoncross]

Instead of manually trying to buffer an entire email message into RAM and then process it consider using https://github.com/emersion/go-smtp who has built (from what I can see) the world's best OS Go email parsing libraries (MIME, DKIM, SMTP, etc...) already including full streaming support for MIME envelope creation and parsing and textproto for decoding/encoding.

I personally tried to beat his package forking Mark Hale's https://github.com/Xeoncross/smtpd (which he forked from Brad Fitzpatrick's go-smtpd) to support streaming support via a custom https://github.com/Xeoncross/mimestream implementation and still failed to reach proper performance.

Please, consider abandoning your current SMTP library for this streaming performance-orientated SMTP server/client. Lets try to reduce the duplicated work needed for important projects like personal email servers. I'll try to add your library to my benchmarks when I get a chance to show the gains you could have.

Also, note that you might be able to borrow ideas from https://github.com/emersion/maddy and https://github.com/foxcpp/go-imap-sql