dnsmx - recursive lookup of MX records for fqdn
dnsmx fqdn
If there are no MX records, dnsmx prints an artificial MX record, simulating the behavior of MTAs.
dnsip(1), dnsname(1), dnsipq(1), dnstxt(1), dnsqr(1), dnsq(1), dnstrace(1)
http://cr.yp.to/djbdns.html