from
The Free On-line Dictionary of Computing (8 July 2008)
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 "[email protected]" 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)