AfterLogic XMail Server is a free open source e-mail server available for Windows and Linux platforms.

Supports ESMTP, TLS/SSL secure connections, SMTP authentication, account and domain aliasing, anti-spam features (IP-based and e-mail address based),mailing lists, logging, remote administration, Finger protocol, filters, custom mail processing, simultaneous multi-user access to a POP3 mailbox. AfterLogic XMail Server is based on open source XMail server.

The advantages of AfterLogic XMail Server against original XMail include simultaneous multi-user access to a POP3 mailbox, configuring port numbers via config file, handy Windows installer. The product is shipped under GPLv2 terms for many 32-bit platforms including Windows NT/2000/XP/2003/Vista, GNU/Linux, etc.