I'm in the final phases of moving a buttload of domains (mostly friends and family email) from WF to OS.

tl;dr: mx1.us.opalstack.com does not appear to be using OS DNS servers, or at least not checking them first, because it is sending email to WF, not to the OS.

Backstory to explain the problem.

I can check my domains' DNS using (from the command line):
dig @ns1.us.opalstack.com -t mx oneofmydomains.com
and get the expected mx1.us.opalstack.com, etc. Note: putting the '@' in there tells dig to use that specific DNS server, not just any one that is handy.

So I know the OS DNS servers have the right stuff. I can check my websites by changing the DNS on my desktop to using ns1(or 2).us.opalstack.com and things look good. I also know that opal3.opalstack.com Apache server is using the US OS DNS because I have a domain that does a redirect and it is handled correctly. I know it's not the WF site because I stick a "Hi, Mom!" in the top of the OS index page for that domain.

I can check mail forwarding to gmail accounts by using smtp.opalstack.com and it arrives where expected.

The problem happens when I try to send mail to an address that maps to a mailbox on OpalStack. E.g. Email to peter@mydomain.us (my real address) is sent to WF, not stored in my mailbox on OS. This would appear to mean that the SMTP server is not using OS DNS. Weirdly enough, if I send email from the command line on opal3, I get the same problem. Is the Apache server using different DNS servers than the shell on opal3?

I'm guessing that since the OS DNS servers do not allow recursion, the SMTP server uses some DNS that does allow recursion, and that means it finds the current DNS for my domain, not the OS DNS.

I really like to check things from A to Z before cutting over about 25 domains. Most of my friends and family have Clue Zero about any of this stuff, and if I can't check things first it will lead to many looong AnyDesk sessions to try and get them setup correctly.

I've had too many beers to try and figure this out tonight.

TIA