How to licence a virtual machine on physical server 2008 R2, if i want to make that virtual machine mail server with MS Exchange 2010?

Check out the two articles from Microsoft and let me know if doesn't answer your question.

http://www.microsoft.com/licensing/about-licensing/virtualization.aspx#tab=2

http://www.microsoft.com/en-gb/licensing/about-licensing/virtualization.aspx

Regards

Qazzafi

Does it mean that with one Enterprise Edition which is licensed to physical server can hold up to four Virtual machine and all these four VM's will be licensed with that one Product key applied to physical server, or we have to purchase another product key for registering that VM's and need extra licensing ?