comments were converted to a solution below.

I tried using the apt package to tinydns and get the same problem.

I'm seeing the same issue on Ubuntu 22.04.4. Did you find a work around?

Then why doesn't this happen with any other device. I have many drives and SSDs that accurately show the lifetime in hours when a test is run. for example: # 1 Short offline Completed without error 00% 48288 -

Edited to include smartctl -a

I think creating such a rule in sendmail would be complex. I switched to 'qmail' long ago which has more straightforward configuration which could do what you want, however I think converting from sendmail to qmail is beyond the scope of what you are looking for.

Actually the link explains how to set up authenticated NTP, which would solve his problem as revised by the comment thread.

The CentOS machine (if compromised) could be used to attack (try to find security flaws and access) the RHEL machines on the same subnet. Being on the same subnet allows it to talk to those machines without going thru any firewall and thus would make it easier to exploit them. The RHEL machines would only have local firewalls (ipchains, ipfw, ...) to prevent intrusion, if there are any setup.