The Exchange 2010 RTM (Release To Manufacturing) build has now reached the end of its support lifecycle. Customers should upgrade to SP1 to continue to receive support (amongst many other good reasons!).
The Exchange 2010 lifecycle can be viewed here:
Full details about the Microsoft lifecycle policy can be viewed here
http://support.microsoft.com/lifecycle/
I would also encourage you to sign up to the quarterly lifecycle update newsletter to ensure that you have the knowledge to keep all of your products in a supported state, and continue to receive the support that you are entitled to!
Cheers,
Rhoderick
