From The Free On-line Dictionary of Computing (19 January 2023):
Mail Exchange Record
MX
MX Record
<messaging> (MX Record) A DNS resource record type that says
which SMTP server handles electronic mail for a particular
domain. E.g. the MX record
foo.co.uk. 1054 IN MX 10 mail.foo.co.uk.
means that mail for an address like "denis@foo.co.uk" should
be sent to "mail.foo.co.uk".
There can be several servers for a domain. The "10" is a
priority - the server with the lowest number will be tried
first.
(2007-01-29)
From The Free On-line Dictionary of Computing (19 January 2023):
mx
<networking> The country code for Mexico.
(1999-01-27)