Powershell – Reinitialize a single Exchange 2010 mailbox

You need to give the Exchange Trusted Subsystem read/write access to the folder that contains the PST. Try again after adding this to your ACL on the pstfiles folder.

Spreading out your mailboxes across databases is good to keep database sizes low. If anything goes seriously wrong and you have to run offline utilities to get things back, you will thank yourself for keeping smaller databases. Users do not like being without email for the 8 hours it takes to recover a 25GB database.

As for targeted moves, there is a way to move users into specific databases. We did this when we did the 2003 > 2007 move. I believe you need to use Exchange 2010 tools to do the migration, and you can pick the target database. We used a PowerShell script to perform the migrations, which may expose a few more controls to manage this.