Zenity - Zenity is a tool that allows you to display GTK dialog boxes in commandline and shell scripts.
Spamihilator - The free Anti-Spam-Filter Spamihilator removes more than 98% of spam mails before they even get into your inbox.
Glade - Glade is a RAD tool to enable quick & easy development of user interfaces for the GTK+ toolkit...
SpamAssassin - Use this program to "Unspam" your mailbox(es).
Yad - Yad (yet another dialog) is a fork of Zenity with many improvements, such as custom buttons...
SPAMfighter - SPAMfighter and Microsoft have built the strongest and most effective anti spam filter for Outlook, Windows Live Mail, Outlook Express & Thunderbird