user indestructable @ instructables.com have build this project that is able to flash a led when there is an email on your email server. He writes:
The idea behind the eMail Light project is to indicate the presence of emails that are currently on my email server with a flashing LED. I am often not right at my desk and I would like to know if I have email. Or I am near my desk, but my screen saver has kicked in while I’m working on something that doesn’t involve a constant mouse wiggle. By making a little black box with LEDs that can be controlled by USB through a mail monitoring program, I can be alerted to the presence of email on my server.
eMail Light: LEDs show new email - [Link]