Someone deleted one or more mailboxes and you want them back.
For Exchange Server 2003:
Open the Exchange System Manager (Exchange System Manager.msc).
Expand the Tools node and right-click the Mailbox Recovery Center node.
Select the Add Mailbox Store command. The Add Mailbox store(s) dialog box will appear (see Figure 5-2).
Enter the name of the mailbox database that formerly contained the mailboxes you want to recover; there's no way to browse them. However, you do not need the name of the server or storage group that hosts the mailbox stores in question. You can use the Check Names button to verify that you've entered a valid database name. Click OK when you're done; ESM will update its right pane and list all deleted mailboxes that are still present in the store.
If you don't see the mailbox you want to recover, that means that it's gone past the deleted mailbox retention period specified on the database or that it's actually in a different database. If you do see it, right-click it and select the Find Match command. This starts the Exchange Mailbox Matching Wizard; click Next and the wizard will attempt to match the mailbox to the account formerly associated with it.
The completion screen of the wizard will appear; click Finish after verifying that the mailbox was connected to the right mailbox. If it's not, you'll need to right-click the mailbox and choose the Resolve Conflicts command, which shows ...