SpamAssassin headers show "URIBL Blocked" error when Exim uses RBLs

Symptoms

An error message similar to the following appears in the headers of a message when Exim is configured to use an RBL (Realtime Blackhole Lists).

0.0 URIBL_BLOCKED ADMINISTRATOR NOTICE: The query to URIBL was blocked.
See http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block for more information.

Description 

This error appears when the nameservers in the /etc/resolv.conf file are not permitted to perform DNS lookups to the URIBL servers.

Workaround

Change the nameservers in the /etc/resolv.conf file from a public DNS provider (such as OpenDNS or Google) to your local data center's nameservers. If this does not resolve the issue, you may need to use your own recursive DNS servers.

Additional resources

How to edit your server's resolver configuration via WHM or SSH.