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SpamAssassin 4.0.0 changed to use a different internal module to handle IP address country lookups. This is mentioned in the release notes at https://github.com/apache/spamassassin/blob/trunk/UPGRADE but the configuration changes required are not specified anywhere that I could find - the release notes mention the new names of the required options, but not their expected values or syntax. I ended up having to look at the source code in order to work out how to continue using DBFile. I've updated the article to include the new syntax. Hopefully this is useful! Without it, SpamAssassin will fail to upgrade cleanly when upgrading Debian Bullseye to Bookworm.