A Mail Exchanger or MX, record designates the host name and preference value for a mail server or exchanger, as defined in RFC 974.
An MX record requires a name and a priority value. Priorities with a lower numeric value are chosen first in assessing delivery options. You can set the time-to-live (TTL) for this record to an override value, so that the record has a longer or shorter TTL. A comment field is also included.
This method attempts to link to an existing host record. If an existing host record cannot be located, the method attempts to link to an existing external host record. If neither can be located, the method fails.