Sometime in the last few days,
Spamhaus seems to have started issuing a block message if someone queries the DBL with an IP address. folks started seeing an uptick in error messages that mention Spamhaus saying:
554 5.7.1 Service unavailable; Client host [x.x.x.x] blocked using dbl.spamhaus.org; No IP queries, see https://www.spamhaus.org/faq/section/Spamhaus%20DBL#279 (in reply to RCPT TO command))
Crowdsourcing information from the emailgeeks slack channel makes it look like sometime in the last 2 or 3 days
Spamhaus started replying positively to any query of the DBL that was an IP address changed their DBL configuration are querying the list incorrectly. Spamhaus has always returned this code to senders querying the DBL with an IP address.
Basically, anyone who is getting this error message can do nothing about it. This is a configuration error on the receiver’s side. If it continues for much longer, I’d mark the domains as inactive and do not mail. Clearly no one at the domain is home and haven’t noticed they’ve not received any email in days.
Many thanks to Spamhaus for contacting me and setting me straight that this was nothing new and the DBL has always returned 127.0.1.255 to an IP query directed at the DBL.