DNS timeouts go away when bypassing UTM

Hello,

I'm running a Sophos Home appliance here which is doing DNS and DHCP for the whole network.

Now I am having trouble with DNS resolution.

I always get two timeouts when I do nslookup from my computer to google.de.

If I change the nameserver in the command to cloudflare (1.1.1.1) I receive an instant answer.

So something is going wrong. I followed BAlfsons DNS best practice guide but the problem persists.

I am running DNS with an availibilty group that contains Googles and Cloudflares DNS servers.

Additionally I have a request route for office365.com.

Clients have the UTm as primary DNS server and 1.1.1.1 as secondary.

This all works, but I am experiencing significant delays when I am browsing the internet. I turned of Intrusion Prevention but that did not do the trick.

Any ideas where I would have to look for further misconfiguration?

Thanks,

Tim