I have a sender who sends from a domain with a null MX set to localhost. Exim returns a 451 loca temporary failure because the dnslookup router defers the mail (lowest mx points at localhost).
I would expect some form of 500-type error returning.
When I send a mail to that domain it also gets defered and frozen. Again I would expect some error.
What setting do I have to make in the dnslookup-router that a “MX 0 localhost.” fails and not defers?
