A Domain Alias is an alias for a secondary domain name that points to an existing email account on the server under an existing primary domain name.

For example, a full email addresses requires a user name and a domain name (ex. user@example.com). If you add a domain alias on a secondary domain like "example-alias.com" then not only will "user@example.com" be valid, but the same mailbox will also work with "user@example-alias.com". If an email was sent to both emails then the "user" mailbox would get two copies of the emails.

A user cannot log into the web interface under a domain alias, just the original domain, nor can a user send an email from the domain alias. Remember, any alias is simply a pointer to an existing email account on the server.

Notes:

• Messages can not be retrieved with a domain alias email address unless the domain is properly registered at a domain registrar.
• The mail exchange (MX) record for the domain being added must already be pointing at the server prior to this process. This prevents users from 'hijacking' mail from valid domains. For example if this check were not in place a user could add a domain alias of example.com. Then, any mail sent from the server to "anything@example.com" would go to the domain with the example.com domain alias, rather than to the actual domain.