Moving mailboxes to an Exchange 2007 server is a time consuming task in an inter-forest migration and you can only use the move-mailbox cmdlet. By default, you can only move 4 mailboxes simultaneously. This makes things very difficult if you have thousands of mailboxes to be moved.
You can increase the number of mailbox move threads from 4 to a maximum of 30 by adding a switch to the move-mailbox cmdlet. Run the command
Get-Mailbox -Server CurrentServerName | Move-Mailbox –TargetDatabase “NewServerSG1DatabaseName” –MaxThreads 30
Though you can specify any value between zero and 30, make sure you give an appropriate value depending upon your network.
Good to know. Will help in my migration work.
-Martin