When a domain is blocked by DNS, it is blocked by the DNS in the Access Control profile.

Unless the domain is whitelisted. For a white listed domain, the DNS lookup falls back to the system DNS service, which is the DNS in Internet Settings (or DNS under the Internet section on the Status page, which is the same).

You’ll get blocked by DNS either because the domain is blocked, or it doesn’t exist. The router cannot tell them apart because the response from the DNS service is the same.

In your example above, the domain flightproxy-euno-01-teams.cloudapp.net doesn’t exist for several DNS services. You can try it here: https://mxtoolbox.com/SuperTool.aspx (select “DNS Lookup” in the orange dropdown). Whitelisting it does not make it available.

The domain flightproxy-euno-02-teams.cloudapp.net should work fine.