Scenario:  Restore user account where the account was accidentally/ purposely deleted and the mailbox resides on an Exchange 2010 in a mixed 2003, 2008 environment. The deleted mailbox is now showing in disconnected mailboxes.

The first step is to recover the deleted user account in AD. Hoping that you have left the tombstones on the server to either 60 days or 180 days which is the default for windows 2003 and up.

There are several ways too restore the account, the most painstaking one using system state restore after booting into directory services restore mode which means downtime.

The easiest and simplest way is using adrestore CLI available from Microsoft, if you need GUI adrestore.net is the best.

Download it from the link and install on the DC.

Adrestore.net

The how to is available from the developers site http://blogs.microsoft.co.il/blogs/guyt/archive/2007/12/15/adrestore-net-rewrite.aspx and http://www.petri.co.il/recovering-deleted-items-active-directory.htm

Now that you have restored the user account the next problem is to connect the disconnected mailbox which is rather easy, just open EMC 2010 right-click on a disconnected mailbox, select Connect and choose a matching user in this case.

If the online maintainence hasn’t run then the deleted mailbox will not show in disconnected mailbox, you will need to run this command in PS

Clean-MailboxDatabase databasename

And now you can connect the mailbox to the user you just restored