For Example: If you have multiple domain aliases such as domain1.com, domain2.com and domain3.com.... upon creation the selected domain.com or primary smtp domain within the list will be the primary domain and will not inherit domain2.com or domain3.com.
domain1.com
domain2.com
domain3.com
Mailbox Aliases:
1. Under My Users, Select the User List to populate all mailboxes.
2. Choose the user you wish to edit and Select Edit User at the top.
3. Under the Microsoft Exchange tab, navigate to Manage Alias.
4. Add the user aliases you would like to be associated with that particular mailbox such as user@domain.com, choose Add Alias and Save Changes
Distribution List Aliases:
1. Under My Current Services, Select Distribution Lists.
2. Choose the Distribution List you wish to edit and click Edit Distribution List at the top.
3. Under Manage aliases, add the DL aliases you would like to be associated with that particular distribution list such as: info@domain.com, Add info@domain2.com (located in the drop down list) and choose Add Alias and Save Changes.