If you wish to use a remote Mailserver, a few changes will need to be made.
1) Go to User Panel -> domain.com -> Email -> MX Records
There should be an option for "Local Mail Server". Â Uncheck that option.
2) You'll need to change the MX dns record to point to the external mailserver. Â Remove the "mail" MX record and add "other.domain.com." as the new MX record where that is the domain of the other server.