mail nitification in menu bar

is there any way of getting an unread email counter in the top menu bar?

I don't think there is, there might be some tweaks out there. Have you tried Growl? I think that's compatible, also when you get unread emails a little red circle with the number of unread emails shows on the Mail icon (providing the program's active with the dot underneath it).

There are a few utilities that will allow you to do this:

New Mail Notification in the Menu Bar! | New Mac User

This is a good place to start.