I'm also getting this exception when I connect via VPN to my office. My code tries to get TXT record instead of MX. I do not understand why, but adding , tcp = True solves my problem.

Try to add this parameter to the end of resolve function:

dns.resolver.resolve("cmrit.ac.in", 'MX', tcp = True)

PS.

1. Adding , lifetime=10 also solves the problem, but it waits answer too long.

2. When I tested getting TXT record through nslookup:

nslookup -q=subdomain.example.com

, I have noticed that there were no nameserver-list in output when I use VPN.

Maybe someone can explain this behavior?