DNS Lookup Outsourcing?

[Will]

Is there a large DNS vendor to whom a small company can outsource DNS
lookups?   We have constant problems with doing smart lookups on our mail
server, and rather than debug everyone else's (and our own) DNS
configuration errors, I would rather have our DNS servers do forwarding to a
commercial vendor who specializes in DNS.   If we have problems resolving a
particular domain's DNS records, I would expect to be able to make it the
vendor's problem to resolve that in a few days rather than it being our
problem.

We can of course forward DNS lookups to our ISP, but their technical support
people are so hopelessly clueless I would rather just pay extra money to
someone who is a specialist, has a first-grade network, and can deliver
specialized support around DNS lookups.

-- 
Will