At least one ESP and Spamhaus are currently investigating bounce messages at a couple ISPs incorrectly pointing to Spamhaus as the reason for the block. The bounce messages are taking the form:

smtp; 554 p3plibsmtp03-07.prod.phx3.secureserver.net bizsmtp IB105. Connection refused. 192.0.2.24 is
listed on the Exploits Block List (XBL) <http://www.spamhaus.org/query/ip/192.0.2.24> Please visit http://www.spamhaus.org/xbl/ for more information.
smtp; 553 5.7.1 [BL21] Connections will not be accepted from 192.0.2.59 because the IP is Spamhaus’s list; see http://postmaster.yahoo.com/550-bl23.html
smtp; 553 5.7.1 [BL21] Connections will not be accepted from 192.0.2.136, because the ip is in
Spamhaus’s list; see http://postmaster.yahoo.com/550-bl23.html

The IPs involved are not listed on any of the Spamhaus lists. It looks like there’s some corruption somewhere. I’ve heard about this from a couple different places, so if it’s happening to you it’s not just you. It’s also being addressed by people who can fix it.

filtering • rejection • sbl