Note: These examples should work on *nix boxes since they generally make use of Posix commands.

The following example is kindly provided by coffy from the german Nagios forum:

• First parameter: domain which MX record should be checked
• Second parameter: mail server to serve this mail domain

check_generic -n mx_dns -e "nslookup -querytype=mx $ARG1$ | grep 'mail exchanger' | awk '{print \$6}'"  -c '!~/$ARG2$\./'