before migrating to 22.04, I did a reinstall test and I had chosen the default name for the box (box.domainame). I also pointed DNS etc to do the test.
When doing the proper install, on a new fresh machine, I instead used my usual name for the box (mail.domainname).
After 6 days, then I run the STATUS page, I randomly get the below:
The nameservers set on this domain at your domain name registrar should be ns1.mail.xxxx.yy; puck.nether.net. They are currently ns1.box.xxxx.yy; puck.nether.net. If you are using External DNS, this may be OK.
Like if the box.xxxx.yy was cached somewhere…I cannot really understand where…I tried dig, nslookup etc with no luck, this is totally random
While reviewing the OP’s zone files, I noticed that the SOA records on the master and the slave were different. Puck had the old hostname while the master was of course up to date. The bizarre part was the both had identical serial numbers.
The solution was to add a record (temporarily) so that the serial number changed leading to an update of the slave.
I suspect that this may have happened when the OP changed the box’s name. I am not sure why the box wouldn’t have updated the serial number though.