I have 2 domains, both with VS properties on VirtualMin.
Mail for domain A is hosted on VirtualMin, while only the website for domain B is hosted there.
The mail for domain B is hosted elsewhere.
When A tries to sent B a message we get a 550 5.1.1 failure.
I’m sure there’s an option to force it to use DNS to route the mail but I can’t find it anywhere (have tried Google )
Is it wise to reconfigure the entire server just to address an issue with one domain? Have you considered the impact this will have on the efficiency of other services? E.g. DNS lookups for antispam.
One non-intrusive way to solve the problem would be to configure domain b correctly in Virtualmin. Edit Virtual Server and uncheck the box for mail for that domain / virtual server.
Another way to address the issue would be to route mail correctly. Edit DNS records for domain b so that the MX in Virtualmin DNS is made identical to the one in the DNS records for the domain that is hosted externally.