1. Login into your Web Panel.
2. Select Domain Names from left panel and click on “Add New Domain” button
3. Enter the domain name.
For example: demoadmin.com.
4. Click on “Add Domain”.
5. Go back to your Exchange Control Panel and you should be able to see the domain in the dropdown when creating users and so on.
NOTE: You may need to logout and login again in your exchange control panel.