SeaMonkey is the successor of the Mozilla Suite. The mail client allows connections over POPv3 and IMAPv4. In some cases one wants to leave the program running for longer periods of time, but once the mail client has password for a mail server it just stays connected. In case of "keep everything on server" profiles this means that the mail may stay accessible even when the machine is left unattended (which it often is). The purpose of the extension is to enable requesting the client to forget mail server passwords, so that the mail is no longer accessible without entering it again.

http://www.seamonkey-project.org/