dnsmx — look up the mail exchanger records of a domain name
dnsmx looks up the MX resource records for
fqdn in the Domain Name System, and prints them.
If there are no MX resource records, dnsmx prints an artificial MX record, simulating the behavior of MTAs.
Normally dnsmx exits 0. If it encounters a temporary problem that prevents it from determining the MX resource records, it prints an error message and exits 111.
dnsmx makes all DNS lookups using the locally configured DNS proxy server. See dnsqr(1) for how this server is found.