Moving mailboxes from one database/server to another is fairly easy. I prefer to use the shell interface but you can also use the GUI.
The following commands are handy :
New-MoveRequest -Identity <mailbox> –TargetDatabase <targetdatabase>
(This commands moves one specified mailbox to another database)
You can also use to move mailboxes from one database to another with the following command :
Get-Mailbox -Resultsize Unlimited -Database <SpurceDatabase> | New-MoveRequest -TargetDatabase <targetdatabase>
Often I use the following command to move all mailboxes from one server to another server :
Get-Mailbox –Server <servername> | New-MoveRequest –TargetDatabase <targetdabase>
It’s also possible to use a where statement (example which OU) :
Get-Mailbox -Resultsize Unlimited | Where {$_.OrganizationalUnit -like “*sales*”} | New-MoveRequest -TargetDatabase <TargetDatabase>