If you have BES and Exchange 2010 SP1 RU2 hold on...do not install the RU3!!!!!!
From the EHLO blog :
We have received notification of an issue impacting some customers which have RIM BlackBerry devices connecting to an Exchange 2010 SP1 RU3 environment. At this stage we are actively working with RIM to identify the exact scenarios in which customers are reporting this issue in order to narrow down the root cause of the problem and identify a suitable resolution for it.
As a precautionary measure we have deactivated the download page for Exchange 2010 SP1 RU3 until we can identify the appropriate next steps.
If you are a customer seeing duplicate messages being delivered when an email is sent from a BlackBerry device and you have RU3 installed within your Exchange 2010 environment, our recommendation is to contact Microsoft Support for assistance in troubleshooting the issue you’re experiencing.
The full article http://blogs.technet.com/b/exchange/archive/2011/03/14/exchange-2010-sp1-rollup-3-and-blackberrys-sending-duplicate-messages.aspx
I 'll keep you posted..