Using the unix dig
command, I can get the following MX record:
$ dig +nocmd gmail.com MX +noall +answer gmail.com. 1868 IN MX 20 alt2.gmail-smtp-in.l.google.com. gmail.com. 1868 IN MX 40 alt4.gmail-smtp-in.l.google.com. gmail.com. 1868 IN MX 5 gmail-smtp-in.l.google.com. gmail.com. 1868 IN MX 10 alt1.gmail-smtp-in.l.google.com. gmail.com. 1868 IN MX 30 alt3.gmail-smtp-in.l.google.com.
My question is, what does the fifth column (20, 40, 5…) mean?
Best Answer
The numbers give the relative preference of the MX records. Lower values are more preferred. See RFC 1035