If Spamassassin is reporting the following:
0.0 URIBL_BLOCKED ADMINISTRATOR NOTICE: The query to URIBL was blocked. # See # http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block # for more information. # [URIs: example.org]
then you can check whether your dns forwarder is possibly blocked by URIBL:
$ host -t TXT 188.8.131.52.multi.uribl.com # 184.108.40.206.multi.uribl.com descriptive text "Too many queries from 220.127.116.11. See http://uribl.com/about.shtml#abuse. Emails blocked due to this response are done so incorrectly. Please fix your software."
The server in question is running at Hetzner and 18.104.22.168 seems to be Hetzner’s front-end forwarding DNS server. Since we’re using Hetzner’s default DNS servers as most of their customers, it seems like the result is too many lookups to URIBL and in consequence URIBL blocking lookups from Hetzner’s.
So either you can install your own DNS forwarder, or pay for URIBL’s service, or you can stop using the service. The later would be in /etc/spamassassin/local.cf:
score URIBL_BLOCKED 0
Article by Tomas Posíšek firstname.lastname@example.org