Follow these steps to set an alias for Rackspace Mail:
1. Log in to Cloud Office Control Panel
2. Click Aliases in the Rackspace Email section.
3. Click on Add Alias
4. Choose appropriate domain name.
5. Enter alias in the Create New Alias box.
6. Select one or more mailboxes from Members inside this Domain box and click Add to add them to Members of this Alias box.
7. Up to four external addresses for domains like Hotmail, Google or Yahoo can also be added.
8. Click Save.