A while ago I added a new anti-spam technique to my mail server setup called “No Listing”. No listing basically means putting a high priority MX record in the DNS that always rejects mail server connections.. It seems, however, that the qmail mail server can’t cope with that. It’s not RFC compliant.
(Read this entire post, as there is a very weird problem described later) It’s been quite a while since I upgraded the hardware that runs this (and others) web site. The warranty on the systems either will be expiring soon or has already expired. So I bit the bullet and ordered a new Dell PowerEdge …