[Samba] Samba AD Internal DNS, Postfix & Email Relay

[Marco Shmerykowsky]

Is there an extra step which must be taken to get postfix
to deliver email via a relay host when the postfix machine
is pointing to an samba internal DNS?

I did a test setup using a public DNS server and it worked.
Same setup where the machine (Debian 9) is pointing to a
samba DNS doesn't work.  The errors in the postfix log
seem to be DNS related.

Thanks,