RadicalSpam is a free and open source package distributed under GPL v2, including products such as Postfix, SpamAssassin Amavisd-new, Clamav, Razor, DCC, Postgrey, Bind; providing a secure SMTP relay, ready to use with linux and docker environement. More information : http://www.radical-spam.org
Another distribution of apache that contains Apache, MySQL, Perl, and PHP. and comes with the following modules mod_perl, mod_php, mod_python, and more. Also Contains a FTP and Mail Server. Will be ready to run right after installation and a reboot.
PyWebMail is a Python library and POP3 gateway that enable working with WebMail servers like with POP3 or IMAP mail server. Currently Mail.Com, Yahoo! Mail, Gmail, Netscape.Net, HotMail and some minor servers support is finished.
mailgate is a set of Python scripts we used at my former company to transfer email a) from a POP3 account to our internal mail server, b) from a POP3 account to a mailbox file and c) from a mailbox file to a SMTP server.