I've updated the XNND DNS lookup tool so that it you can now select "Multi DNS = yes" and the tool will now make the same DNS query against a number of different public DNS servers all in a row.
It'll help you catch issues where you've perhaps updated a DNS entry but are waiting out the TTL (DNS cache) and want to check to see what different servers can see. It can also help you identify some kinds of intermittent DNS issues. I've already run into a couple of different scenarios where I've found it quite useful. I hope you'll find it useful, too!
Example query: Look up the MX records for spamresource.com against all available DNS servers.