I have one domain that we send to that is giving us kickbacks and returns this error:
550 5.0.350 Remote server returned an error -> 571 Delivery not authorized, message refused
I have looked at all my stuff and sent emails to other domains with no issues.
The tech at that location said it is on my end, and of course, I said it can't be because you're domain is the only one kicking back emails.
Any ideas? The research he did said I should change my domain in exchange to Internal Relay but that doesn't make sense as we aren't sharing a domain or in a hybrid state with that domain.