Server not receiving external email while outgoing one work fine

Hi ZeAntwan,

Was Gmail on the sending or receiving end? Maybe Gmail silently drops the error? I have no experience with them, but Gmail is not said to be very friendly towards home-hosting.

I recall recently someone started a thread that seems to be from “the other side” of the problem.
Edit, Recption email impossible

The point was that the hoster (could be OVH, or another large hoster) was freeloading on Spamhaus’ infrastructure, or something.

Spamhaus got sick of it, and would designate any “Is this mail spam?”-question from the network in question with “I’m not sure whether it’s SPAM, but you have to pay up or request a small-use API-key to get a better indication”. Since the answer includes “SPAM”, the message got sent back to the sender (poster of the thread in this case).

I think the Spamhaus page explaining the case is DNSBL Error Code - Open/public resolver - The Spamhaus Project