gbiff2 periodically checks for mail and displays headers when new mail has arrived. It relies on the GNOME and GTK libraries, but can be compiled and used with or without GNOME support. The protocols it supports are POP3, APOP, IMAP4, mh, qmail, and mailfile. Furthermore, gbiff2 is fully configurable, with a lot of options like polltime, poptime, sounds, mail reader, mailbox title, etc.
