All certificates are up to date.
Both these errors are now going on Day 3 without being resolved.
I had run both the mailinabox reinstallation script (followed by reboots), as well as the dns_update --force previously, to no avail.
I’ve also tried to turn off IPv6 (the prior box being migrated from didn’t have IPv6, only IPv4), but predictably nsd name services didn’t work then, so I re-enabled it.
Now, emails appear to be working, but these errors persist (also, for some reason, I can’t SSH or ping the VM this is sitting on right now, which is kinda weird, but all email services and web services appear to be working).