For those of you preparing to do an inter-org Exchange migration between Exchange 2010 organizations, the MRSProxy service is a required component that facilitates cross-forest mailbox moves. (Note this process is only relevant when one forest is running Exchange 2010 and the other forest has at least a single Exchange 2010 CAS Server). This service is installed by default, but is disabled. As such, it must be enabled when doing this type of migration.
Microsoft published a definitive KB article on how to do this: Start the MRSProxy Service on a Remote Client Access Server. This article however, explains how to do this with Exchange Service Pack 2 installed. If you are still running SP1 however, this procedure does not work, as the service was updated in SP2.
The procedure for enabling the service prior to SP2 is as follows:
- On the CAS servers in the remote forest, edit the web.config file (the default installation location is c:\program files\Microsoft\Exchange server\v14\client access\exchweb\ews)
- At the bottom of the file is a parameter for MRSProxyConfiguration. Change the IsEnabled=”False” value to “True”
You may also want to update the MaxMRSConnections as well. This value determines how many mailbox moves can be done simultaneously. The default value is 100. This number should be reduced if the mailbox move is going across a WAN link.
The MSExchangeMailboxReplication service needs to be restarted for this change to take effect. This will impact a DAG as this service is responsible for copying the log files to the servers hosting the passive copies of the mailbox databases.