MailMessager is a customizable utility that sits on the Windows or KDE3 system tray and polls email accounts for new email messages. SSL/non-SSL IMAP, POP3, and Atom feed (Gmail) protocols supported. A notification is displayed upon receiving new email.
Adding my Gmail account
Notification - new email on two of four accounts
KDE3 adding my Gmail account
KDE3 tray icon and announcement of new Gmail messages.