Tools
Mail Servers (MTAs)
Zimbra
From the Zimbra site: "Zimbra is open source server software for email and collaboration - email, group calendar, contacts, instant messaging, file storage and web document management. The Zimbra email and calendar server is available for Linux, Mac OS X and virtualization platforms. Zimbra syncs to smartphones (iPhone, BlackBerry) and desktop clients like Outlook and Thunderbird."
Under the covers Zimbra uses the postfix MTA and SpamAssassin (typically). This means that there are many ways you can integrate Message Sniffer with Zimbra including our milter (SNFMilter), a postfix filter script, or our SNF4SA plugin.
A great place to get help with Zimbra is here: http://www.zimbra.com/forums/
Please email support@armresearch.com with any questions.