PUBLIC MARKS from cadu with tag smtp

smtpguard is a tool which controls the flow of email traversing an MTA (Mail Transfer Agent). It is designed to be used on an SMTP server for incoming mail, and currently supports postfix.

hMailServer is a free, open source e-mail server for Microsoft Windows. It supports all the common e-mail protocols (IMAP, SMTP, POP3) and comes with an easy-to-use COM library that can be used for integration with other software. It also has supports for virtual domains, distribution lists, antivirus, antispam, aliases, distributed domains and much more. E-mail data is stored in a database server, MySQL or MS SQL, depending on your choice.

Blat is a Win32 command line utility that sends eMail using SMTP or post to usenet using NNTP.