How do I get the mx records for a domain from *nix command line?
3 options, in order from least to most verbose:
host -t mx mydomain.com
nslookup -q=mx mydomain.com
dig -t mx mydomain.com
The difference is largely a matter of personal preference; I tend to use host, but if you want full details about exactly what you're getting back from the server, dig is the way to go.
dig -t mx mydomain.com will work as well.