Glossary
SPF, DKIM and DMARC
SPF, DKIM and DMARC are the three DNS records that let a receiving mail server verify a message really came from the domain it claims to, and decide what to do when it did not.
SPF lists the servers allowed to send for a domain. DKIM signs each message so it cannot be altered in transit. DMARC tells receivers what to do when a message fails the other two, and where to send the report.
Missing or wrong records are the most common reason a well-written email lands in spam. In one engagement, a single SPF fix moved a customer domain from a score of 50 to 70 on the same checker, before any warmup started.
DMARC is started at monitor-only. Reports are read for a few weeks, and only then is the policy moved to quarantine and reject. Going straight to reject on a domain nobody has observed blocks your own mail.
Questions
Do I need all three?
Yes. SPF without DKIM leaves forwarding broken. DKIM without DMARC gives receivers no instruction. All three, correctly set, are the floor that everything else stands on.
How do I check mine?
email-intel, an open source tool, reads all three for any domain and grades them. The first screen of the plan on this site runs the same reading on the domain you sell from.
This term belongs to the outbound engineering glossary. The practice is defined on the category page.
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