sheffters, I got some feedback from Spamhaus on your problem. Maybe they browse the forum; at least someone contacted me and claimed to be from "The Spamhaus Project" I rewrote their text a bit (they used some word I don't understand but I'm assuming isn't entirely nice). The problem is actually ca...

My servers are also in the UK. I did another test this morning, and nslookup against zen.spamhaus.org now resolves to 64.20.60.106 and 64.20.60.99 . An nslookup of zen.spamhaus.org should not resolve to anything at all, since zen.spamhaus.org is *not* a host (it's a NS zone). Trying to ping or look...

ah ... ... I think the Spamhaus database is being a bit OTT by the looks of things ... ... just had a mail from Halfords (that wasnt spam) ... but spamhaus said it was (gave it 127.0.0.255 response). The response you got was NOT from Spamhaus, we do not have any "127.0.0.255" response code. Our cod...

Just tried an nslookup from the server, zen.spamhaus.org times out. Are you trying to look up an A record for zen.spamhaus.org? That of course will never work as zen.spamhaus.org is not a host (it's an NS zone). If this is the case see: "Missing 'A' record for sbl/xbl/pbl/zen.spamhaus.org": http://...

Are you sure that spamhaus just doesn't sometimes return an incorrect result? That is not physically possible. Spamhaus answers many billions of queries each day, if it returned any incorrect results ever it would cause havoc with mail everywhere. The type of problem experienced by the OP is normal...