elspy is an extension to the Exim MTA that allows Exim users to supply a local_scan() function written in Python instead of C. (Exim's local_scan() API lets sysadmins supply site-specific code for approving/rejecting email messages at SMTP time.)
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.
Working as a courier-mta frontend, QUICA can make a quick and friendly to use mail server. Tasks like creating accounts and forwards can be done easily. QUICA manages domains separately , allowing the delegation of each domain to different people.
ISOS is an e-mail and web server. It is designed for ease of use and provides a quick way to e-presence for small businesses and organizations who lack the experience to benefit from high performance, open source software such as Sendmail, Courier Mail,
FrozenPop is a simple and easy to use POP3/SMTP server. Geared to accommodate multiple domains without having to create individual system accounts, FrozenPop installs < 5 mins. With MySQL authentication, creating users is simple.
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.