RIM updated their Compatibility matrix on December 12th to include the new MAPI/CDO version 6.5.8244.0. It is the recommended MAPI/CDO version for 5.0. SP3. The previous version of MAPI 6.5.8211.0 is still supported.
On December 5, 2011, MS released SP2 for Exchange 2010. RIM still has not updated their Compatibility Matrix but the new MAPI/CDO release last week was probably in response to SP2 for Exchange 2010 release. I will update this post if there are reported issues with BES and Exchange 2010 SP2.
A few days ago Microsoft released a new version of MAPI/CDO. The version number is 6.5.8244.0. I have not seen any RIM Knowledge Based articles concerning this new version of MAPI/CDO nor has the Compatibility Matrix for MS Exchange has been updated with the new version. I will keep you posted.