We used OpenDNS until we sent out an email that linked to SurveyMonkey - the URL was wrong, it said surveymonkye.com
The problem was our QA never caught it, since OpenDNS 'fixed' the request during testing. 24,000 emails later, we were instantly alerted to the bad link.
They clicked the links. But OpenDNS 'fixes' the request from the browser, sending you to the right URL even if you enter the wrong one. That's why QA didn't catch it.
Oh weird. It searches for the most relevant thing and flows through? I thought their nxdomain stuff was just to serve ads, not provide redirects to existing sites.
The problem was our QA never caught it, since OpenDNS 'fixed' the request during testing. 24,000 emails later, we were instantly alerted to the bad link.