This Plugin adds support for the OMEMO Encryption to Gajim.

An elegant, secure, adaptable and intuitive XMPP Client. Available for free on Windows, Mac OSX and Linux.

Swift XMPP client source

Maily Herald is a Ruby on Rails engine that helps you send and manage your mailings.
Think of Maily as a self-hosted Mailchimp® you can easily integrate with your site.
Works with Amazon SES, Mandrill and other email delivery services.