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SpamAssassin will perform many DNS lookups for NetworkTests to significantly improve scoring of messages primarily by DNSBlocklists like Spamhaus, SORBS, etc. This information needs to be cached locally to improve performance and limit the number of DNS queries since some DNSBlockLists have limits on free usage.
NOTE: A local DNS caching server should not forward to another other DNS server servers to ensure your queries are not combined with others. Forwarding to other DNS servers usually often results in URIBL_BLOCKED rule hit hits meaning you have gone over their free usage limit.
DNSmasq Dnsmasq should not be used by SpamAssassin since it can only forward to other DNS servers.
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