No, it doesn't have a pop-up. The icon in the task bar changes, but it's
subtle.
You can change the Windows New Mail sound, to a .wav file of your choice
that may be better heard. I use the old AOL mail sound. Go to Start -
Control Panel - Sound - Sounds
In the scroll box, go to "New Mail Notification"
in the Sounds box, go to where your substitute wav file is, test it, and
click Apply.
The newer Windows Live Mail has an icon that has a bit more distinction, but
no pop-up.
Thunderbird has a very nice pop-up that displays the message subject and
part of the message. You can click on it and open the message immediately,
or ignore it, and it goes away.
http://en-us.www.mozilla.com/en-US/thunderbird/