Ricochet
- A program to automatically trace and report unsolicated e-mail (spam).
- http://www.vipul.net/ricochet/

Samsung Contact
- Samsung SDS's business messaging and collaboration / unified communication product, based on HP OpenMail.
- http://samsungcontact.com/

Signature
- Free, open-source producer of dynamic signatures for e-mail and news postings. Allow signing messages with a different .signature every time.
- http://www.caliban.org/linux_signature.html

OpenMail
- Business-class messaging and collaboration for Linux and UNIX. Supports scheduling and other rich Microsoft Outlook functionality via MAPI, as well as internet e-mail standards like IMAP4rev1 and LDAPv3.
- http://www.hp.com/go/openmail

Spruce
- The GTK+ Email Client
- http://spruce.sourceforge.net/

Mutt E-Mail Client
- Mutt is a text-based e-mail client, similar to Elm and Pine.
- http://www.mutt.org/

Anti-Spam Provisions
- Anti-Spam provisions in sendmail 8.8.Howto guide to configure an anti-spam filter.
- http://www.sendmail.org/antispam.html