I’ve been running MIAB for a few years now, with almost zero problems. But I’ve encountered an interesting situation that I haven’t been able to work around.
I host email for my business and several small clients, and recently I had a client who needed a quick fix to get a registration form on a WordPress site sending email again (unrelated problem with their web server). I don’t host this client’s email, it’s running on Office 365.
I had little time to get their web form working again, so I quickly added a “noreply” address for their domain to my MIAB instance, hooked up their WordPress site to that account via an SMTP plugin, and voila! All is well.
Except now, any time I try to send email from my business address to any address on their domain, MIAB stops the message from going out and instead looks internally for the address, and because I don’t actually host their email, it rejects the message with the error “Recipient address rejected: User unknown in virtual mailbox table”.
And I know the issue is internal, because emailing them from any address not hosted on my MIAB instance works just fine.
I know this is a weird edge case and I probably shouldn’t be doing this on my production MIAB - but is there a way to tell MIAB to ignore this domain internally and route emails externally instead?