Yes, it works fine here too, that's what I've used so far in all 7 builds.
So you could try:
1. Install Incredimail or Windows Live so that it's set as default mail client, then go to Windows Mail and select from it's options that this is the default.
2. create an .eml file , right click - open with, select Windows mail and set it to be the default program for opening .eml files...
Please post back the result , i'm really curious and I dont have windows mail installed to test..