When migrating to Exchange 2010, you will need to move the mailboxes from your old legacy server to the new Exchange 2010 server. When working with large migrations, it may take a very long time to migrate all of the mailboxes with the default move request limit. This article will show you how to increase the limits, allowing you to move more mailboxes at a time, speeding up your migration.
It is important to note that you must work within your hardware limits when increasing the mailbox move request limit.
1. Log on to your Microsoft Exchange Transport Server with Administrative Credentials
2. Open Notepad as administrator
3. Navigate to C:\Program Files\Microsoft\Exchange Server\V14\Bin
4. Open MSExchangeMailboxReplication.exe.config
5. Scroll down to the bottom of the file until you see <MRSConfiguration
6. You will find 4 important values in this section that can be increased
7. Increase the numbers to increase the total simultaneous moves
8. Save the file and close notepad
9. Restart the Microsoft Exchange Mailbox Replication Service
For more information regarding this topic, visit http://technet.microsoft.com/en-us/library/ff963524.aspx