Failure installing SP3 on Exchange 2010
When installing SP3 of Exchange 2010 on a SBS 2011 machine the installation might fail on the mailbox role.
Clear the value inside the following key.
HKEY_LOCAL_MACHINE/Software/Microsoft/SmallBusinesServer/Networking/LeafCertThumbprint
Do not delete the entire key since its needed.
Rerun the setup and it will, if nothing else is wrong complete succesfully.
During the SP3 install I passed all prerequisites but during the actual upgrade it failed at the Hub Transport Role
