I've used DYNDNS for our external DNS for several years. We've been on the 5 qps the whole time. It has suddenly shot up to over 200 qps in the last two months. I had them run a report which shows the traffic coming from google addresses, DYNDNS says it is email related. Nothing on my end has changed. Any suggestions what I should look for? It's going to raise my rates from 50/month to 2000/month. We host our email with Office 365. Any ideas?
I would then further assume that the amount of e-mail you are getting has drastically increased.
I an assuming that "qps" is queries (lookups) per second. If so 200 qps is a LOT of queries, that 720,000 queries an hour.
You could look at other DNS hosting services. Heck I'm pretty sure you could host your own DNS server in a colo for less that $2,000 per month.