README.rdoc

Minimal LMTP Server for Ruby ↑

This project is a minimal LMTP server for Ruby. Ever wanted to stick your Ruby application behind a real MTA like Postfix so it can receive mails directly? This library is what you need.

This library provides a single class, LmtpServer, which will open a UNIX domain socket and listen for LMTP commands on it. You then direct your MTA to deliver the mails it receives via LMTP over the socket opened by this library. The email (and surroundings) will then show up in form of callbacks in your application. To speak in terms of email administration, this library thus implements an MDA (mail delivery agent).

It does not provide a means to actually process the emails you receive, you will receive them as a large string with all the original CRLF line separators included. It is recommended to use a library like mail for that.

Dependencies ↑

None but Ruby’s standard socket library.

Usage ↑

require "lmtp"

LmtpServer.new("/var/spool/postfix/private/ruby-lmtp") do |msg|
  puts "-- Start email --"
  puts msg
  puts "-- End email --"
end

You can find a lot more examples in the documentation of the LmtpServer class.

Security considerations ↑

LMTP (RFC 2033) was not designed to be used over the WWW and the RFC actively recommends against such usage. LMTP contains no authentication and similar security measures; it is only intended to be used in a local, trusted environment, which is the reason why this library only provides UNIX domain sockets for listening and not TCP sockets.

Also keep in mind that this library is fairly minimal. While I think I have implemented RFC 2033 correctly, I have not intensly read RFC 821 (SMTP), which is referenced from the LMTP specification at certain parts. If unusual commands are used over the UNIX socket, unexpected things may happen in form of exceptions. Feel free to report such behaviour as a bug.

The library is not multithreaded. You can threadsafely call LmtpServer#stop, but email messages will be proceeded one by one. If multiple clients connect to the UNIX domain socket, they will be queued and handled after one another. That is, if one client does not quit the connection, the entire server is blocked until the (configurable) timeout value is reached.

While you are at it, check out my (German) Blog.

License ↑

Copyright © 2015 Marvin Gülker

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

  2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.