Understanding Mailbox Behavior

We disable mailboxes for users who are away from the office on extended assignments. Recently, some of these users returned to the office, so we re-enabled their mailboxes. However, the users couldn't log on to their mailboxes until the following day. Why not?

When you disable an account in Active Directory (AD), the Store won't allow access to the associated mailbox (unless you use another account that happens to have delegate permissions). When you re-enable the AD account, the status change might need to replicate to other domain controllers (DCs) and Global Catalog (GC) servers before the mailbox server notices it. Also, the change might need time to expire from the DSAccess cache on the Exchange Server. Aside from that, the Store might not pick up the change immediately, as detailed in the Microsoft article "XADM: Changes to Primary Windows NT Account on Mailbox Do Not Take Effect" (http://support.microsoft.com/?kbid=179065). You can't do anything about this delay; you'll just have to alert users and wait it out.

— Paul Robichaux