Exchange for Hosters
As you know, this feature was removed from the current version of Exchange. There are some features back with Exchange 2010 SP1 back not as we had it in the past with legacy versions.
Now with Exchange 2010 SP2 we will get back functionality on a standard On-Premise Exchange environment.
Read
http://blogs.technet.com/b/hameroff/archive/2011/08/08/so-you-want-to-host-exchange.aspx
and
http://blogs.technet.com/b/exchange/archive/2011/08/30/exchange-server-2010-sp2-and-support-for-hosting-exchange.aspx