Configuring User Email Addresses
(Exchange 2007 & 2010)
To configure user email addresses in Exchange 2010 or 2007, open the Exchange Management Console. Expand the left-hand navigation tree to Microsoft Exchange On-Premises, Organization Configuration, Recipient Configuration and select Mailbox.
Double-click the mailbox to modify the email addresses.
Click the Email Addresses tab. The list of email addresses under the heading SMTP shows all of the addresses which the user will be able to send as using Exchange Custom Sender. Use the Add button to add a new SMTP address.
The default address is the one shown in bold.