GMail POP?

[Alex]

I wouldn't want to open emails in a new window so I didn't know that. My middle button does nothing but lock the scroll wheel so that I can scroll by moving my mouse rather than spinning the scroll wheel.

Shift-clicking on a message link will open it in a new window (though you'll have to tell the Firefox pop-up blocker to allow it). I don't know if there is any way to do it with just the mouse.