We are in the process of planning for mailbox archiving for our Exchange 2010 Standard environment. Our goals are to implement a 45 day retention policy, so anything that is older is moved to their archive mailbox. We have a fairly large environment currently, with 5 databases in a DAG, each around 1Tb in size and about 1700 mailboxes. I had specific questions about the behavior of enabling such a retention policy in such a large environment, and how it would behave? Once the policy is in place, what course of action is taken by Exchange to move mail - is it done on a per mailbox basis, where it will process one mailbox then move to the next or will it be doing this to all mailbox simultaneously? If it is multiple, is there a default max limit, or is there a away to limit a range to be performed simultaneously? Also any other caveats to watch out for with this process?