User's E-Mail Aliases (alternative mail names) 

Users->AddUser->UserAlias

When you create a user on the Server you give them a Mail Box name and an e-mail name, both of which are in fact valid e-mail addresses. If a user needs to be able to receive e-mail under further names, they can be set as e-mail alias names.

To set a user alias, go to the Users section by clicking the Users button from the main button bar, then click on the user who needs the alias. You should now see the selected user in a User Configuration Window. The third button in the Tool Bar has a picture of a user wearing dark glasses .  Click on this button to display the Add User Alias window. You can now add aliases by typing in the required name and clicking the Add button.

Users can also receive e-mail under alternative names if they are included in any Internal or External Mailing Lists.