Using SpamAssassin on Windows
How can I install SpamAssassin on Windows? InstallingOnWindows
Commercial Products
Commercial products are listed on the CommercialProducts page.
Open-source Products
Michael Bell has written a HOW-TO on porting SpamAssassin to Win32: http://www.openhandhome.com/howtosa.html
See also: ["WinSpamC"]
Eric Smith wrote a simple VBScript to use SpamAssassin with Exchange 2000. http://www.spamblogging.com/archives/000014.html
Christopher Lewis wrote a much more robust VB ActiveX DLL that enhances Eric's original work, with the added benefit of actually placing the SpamAssassin mail headers in the Exchange mail message. http://www.christopherlewis.com/ExchangeSpamAssassin.htm