Server-side SMTP is Port 25, SMTPS(465) or Submission (587) is commonly used for outgoing mail.
se also: https://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol.
MX records are defined at the place where the DNS zone is administered. The documentation at https://www.godaddy.com/help/add-an-mx-record-19234 appears to be descriptive. In some rare cases the external representation of DNS-data is provided by UCS and https://docs.software-univention.de/manual-4.4.html#networks:dns applies.