Hendrick Software Components has released
Em@ilCRX, software that filters e-mail, traces the source of unsolicited commercial e-mail (SPAM) and reports it. Em@ilCRX costs $29.95 and is available for Mac OS X, Linux and Windows operating systems.
The desktop-based software application does a technical validation of inbound e-mail to detect forgeries. You can filter e-mail by country of origin, use a Regular Expressions (regexp)-based content filter, use a challenge response system if you want, and more.
Em@ilCRX features a rating engine that is based on reverse Domain Name Service (DNS), can be used to automatically accept e-mail from those on a friends list, and can trace and report spammers back to their Internet Service Providers (ISPs).
System requirements call for Mac OS X v10.2.8 or later, 512MB RAM, G3/600MHz or later, any POP/SMTP e-mail client software (including Apple Mail and Microsoft Entourage).