For a long time the answer was no, but developments in the VMware Products have lead to major improvements in disk/network/memory and CPU performance so now the question is…

If your looking for a good starting point I would listen to the recent podcast from the VMware community round table which was specifically on virtualising Exchange..

• Exchange, new Security podcast, and more … Roundtable podcast #31

Also you may want to check out the VMware pages written especially for virtualising Exchange, make sure you check out the resources tab….

• http://www.vmware.com/solutions/business-critical-apps/exchange/

It would seam that after years of advising against it even Microsoft are jumping on the band waggon:

With the release of Microsoft Windows Server 2008 with Hyper-V and Microsoft Hyper-V Server 2008, a virtualized Exchange 2007 SP1 server is no longer restricted to the realm of the lab; it can be deployed in a production environment and receive full support from Microsoft. 

Check out the full article on the Microsoft Exchange Team Blog here