Kris Deugau:
> I think the question is more along the lines of:
>
> "In case some customer changes the MX records away from me, how can I
> automatically stop accepting mail for that domain?"
That is my reading too.
> About the best you can do is probably a cron job that checks on MX
> records for domains you supposedly host, that can lead to automatically
> disabling domains that suddenly point somewhere other than your mail system.
I confirm the above answer.
Postfix does not decide what domains to receive based on MX records.
The SMTP protocol standard does not require MX records, and neither
does Postfix.
Wietse
