Speed Up Exchange 2010 Mailbox Moves

Exchange 2010 CAS servers have a pretty low default of how many mailbox moves can happen concurrently and it's the Mailbox Replication Service (MRS) that sets the throttling. 
Luckily, you can bump up the throttling threshold to allow more concurrent moves and get your migration completed faster!

On each CAS server go to C:\Program Files\Microsoft\Exchange Server\V14\Bin (or your default path if you installed Exchange somewhere else) and open MSExchangeMailboxReplication.exe.config in Notepad. Scroll down to the bottom and under the <MRSConfiguration section, find the strings below:

The defaults will be set to:

 

MaxActiveMovesPerSourceMDB = “5″    

MaxActiveMovesPerTargetMDB = “2″    

MaxActiveMovesPerSourceServer = “50″    

MaxActiveMovesPerTargetServer = “5″    

MaxTotalMovesPerMRS = “100″

 

Change them to:

 

MaxActiveMovesPerSourceMDB = “15″    

MaxActiveMovesPerTargetMDB = “15″    

MaxActiveMovesPerSourceServer = “50″    

MaxActiveMovesPerTargetServer = “40″    

MaxTotalMovesPerMRS = “250″

After you make your changes, restart the MRS (Mailbox Replication Service) service on each CAS server. 
Depending on your IOPs, you can bump the values up a little higher than these and see how things run. If you get errors, bring them back down a bit.

**Note**
After each Rollup or Service Pack, you have to redo the settings because they will be overwritten with the defaults during the upgrade.