MailRun is a small (both in the size of the executable file and the amount of screen real estate if takes up) and fast program to monitor your Pop3 mail account. It is part of NetChat 1.0. Developed by Gary L. Robinson.

Link: http://hobbes.nmsu.edu/h-search.php?key=MailRun_1-23.zip
Thanks to Gary L. Robinson for making it open source.