After adding a new email user from a different account and the domain is not yet set service nsd crashes and can’t recover. Only way to fix it that I could find is rebooting the server and running mailinabox setup command.
Syslog shows:
May 28 16:52:37 ubuntu nsd[29467]: can’t bind tcp socket: Cannot assign requested address
May 28 16:52:37 ubuntu nsd[29467]: cannot open control interface ::1 8952
May 28 16:52:37 ubuntu nsd[29467]: could not open remote control port
May 28 16:52:37 ubuntu nsd[29467]: could not perform remote control setup
May 28 16:52:37 ubuntu kernel: [1211873.404518] init: nsd main process (29467) terminated with status 1
May 28 16:52:37 ubuntu kernel: [1211873.404531] init: nsd main process ended, respawning