1.Click Start, Administrative Tools, and then click Active Directory Users And Computers to open the Active Directory Users And Computers management console.
2.Select the user account object that you want to mail-enable.
3.Click the Action menu and select Exchange Task.
4.The Exchange Task Wizard starts.
5.On the Exchange Task Wizard Welcome page, click Next.
6.Click the Create Mailbox option on the Available Task page and then click Next.
7.Specify the mail store.
8.Specify the server that will host the mailbox. Click Next.
9.Review the displayed summary information.
10.Click Next. Click Finish.

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