Many entries "Deny:DNS Error" in Forward traffic log

Hello everyone, I noticed in Log&Report -> Forward Traffic pretty many (2-3 entries per second) Deny:DNS error. That is what it looks like: On the FortinetGuide Twitter Account I found information: "If you see #FortiGate forward traffic log Deny:DNS Error, it's not the 'gate blocking DNS traffic. It's just not forwarding failed response." https://twitter.com/forti...tus/912853368636366850 But what exacly it is? Why these errors are so much? Mail server is not configured properly? Thanks in advance for your feedback. Regards, Lucas