A user alias is an email address that forwards messages to a list of email addresses. Even though an alias acts as an email address, users cannot login to an alias like they do a standard email address since no email is ever actually stored for the alias. Emails are just sent to the list of addresses provided for the alias. The steps as below:
1. Log into the Postmaster account.
2. Navigate to Domain Settings -> Accounts > Aliases > New
3. Edit as below. Make sure click 'Save' in order for the setting to work
