http://sourceforge.net/projects/courierhttp://www.courier-mta.org
http://www.courier-mta.org/install.htmlhttp://www.courier-mta.org/documentation.htmlhttp://www.courier-mta.org/install.html#webadmin
http://en.wikipedia.org/wiki/Courier_Mail_Server
http://www.lukaszielinski.de/blog/posts/2013/11/02/how-to-setup-a-courier-e-mail-server-with-ubuntu-linux