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A Lightweight High Performance SMTP written in Go, made for receiving large volumes of mail, parse and store in mongodb. The purpose of this daemon is to grab the email, save it to the database and disconnect as quickly as possible.

This server does not attempt to check for spam or do any sender verification. These steps should be performed by other programs. The server does NOT send any email including bounces. This should be performed by a separate program.

The most alluring aspect of Go are the Goroutines! It makes concurrent programming easy, clean and fun! Go programs can also take advantage of all your machine's multiple cores without much effort that you would otherwise need with forking or managing your event loop callbacks, etc. Golang solves the C10K problem in a very interesting way

Once compiled, Smtpd does not have an external dependencies (HTTP, SMTP are all built in).


  • ESMTP server implementing RFC5321
  • Support for SMTP AUTH (RFC4954) and PIPELINING (RFC2920)
  • Multipart MIME support
  • UTF8 support for subject and message
  • Web interface to view messages (plain text, HTML or source)
  • Html sanitizer for html mail in web interface
  • Real-time updates using websocket
  • Download individual attachments
  • MongoDB storage for message persistence
  • Lightweight and portable
  • No installation required

Development Status

SMTPD is currently production quality: it is being used for real work.


  • POP3
  • Rest API
  • Inline resources in Web interface
  • Per user/domain mailbox in web interface

Building from Source

You will need a functioning [Go installation][Golang] for this to work.

Grab the Smtpd source code and compile the daemon:

go get -v

Edit etc/smtpd.conf and tailor to your environment. It should work on most Unix and OS X machines as is. Launch the daemon:

$GOPATH/bin/smtpd -config=$GOPATH/src/

By default the SMTP server will be listening on localhost port 25000 and the web interface will be available at localhost:10025.

This will place smtpd in the background and continue running

/usr/bin/nohup /home/gleez/smtpd -config=/home/gleez/smtpd.conf -logfile=smtpd.log 2>&1 &

You may also put another process to watch your smtpd process and re-start it if something goes wrong.

Using Nginx as a proxy

Nginx can be used to proxy SMTP traffic for GoGuerrilla SMTPd

Why proxy SMTP?

  • Terminate TLS connections: At present, only a partial implementation of TLS is provided. OpenSSL on the other hand, used in Nginx, has a complete implementation of SSL v2/v3 and TLS protocols.
  • Could be used for load balancing and authentication in the future.
  1. Compile nginx with --with-mail --with-mail_ssl_module
  2. Configuration:
mail {
	#This is the URL to Smtpd's http service which tells Nginx where to proxy the traffic to
	server {
		protocol     smtp;

		smtp_auth none;
		timeout 30000;
		smtp_capabilities "PIPELINING" "8BITMIME" "SIZE 20480000";

		# ssl default off. Leave off if starttls is on
		#ssl                   on;
		ssl_certificate        /etc/ssl/certs/ssl-cert-snakeoil.pem;
		ssl_certificate_key    /etc/ssl/private/ssl-cert-snakeoil.key;
		ssl_session_timeout    5m;

		ssl_protocols               SSLv2 SSLv3 TLSv1;
		ssl_ciphers                 HIGH:!aNULL:!MD5;
		ssl_prefer_server_ciphers   on;

		# TLS off unless client issues STARTTLS command
		starttls      on;
		proxy         on;
		xclient       on;



Copyright ©‎ 2014, Gleez Technologies (

Released under MIT license, see LICENSE for details.

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