How to Diagnose Email Spam Issues with SPF, DKIM and DMARC

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Emails landing in spam can often be traced to misconfigured authentication records. SPF is a DNS TXT record that lists which servers may send mail for a domain, and common errors include exceeding 10 DNS lookups, publishing two SPF records, or using the permissive +all mechanism. DKIM requires publishing a public key under a selector record, which should be at least 1024 bits and preferably 2048. DMARC policies should start in monitoring mode with p=none, using reports to refine the setup before moving to quarantine or reject. Additional factors include matching reverse DNS on sending IPs, avoiding blocklists, supporting TLS, and providing one-click unsubscribe headers for bulk mail as required by Gmail and Yahoo. The article also promotes a free external tool that scores a domain's email setup and shows the DNS fixes needed.

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