question DNS Monitoring service

[blogspotter]

What is the most cost effective yet effective DNS monitoring service right now?
If I need to track, say 50,000 names, just for DNS or WHois update?

Thanks in advance

 

[tonyk2000]

Unsure about 50,000 names - but GoDaddy has 100% free domain monitoring (it is located in the same section where their paid backorders are) and they'll email changes (dns, registry whois, exp. dates), if any, 1 time a week or so.

I do not use this feature for domaining business though, just monitoring a few domains which I initially set with retail registrars for my (dentist, accountant etc) and which they are supposed to manage themselves.