SPF, DKIM, and DMARC are related email authentication methods that help receiving systems evaluate whether a message is authorized and whether its visible sender is trustworthy. They are configured in DNS for the sending domain. Correct authentication supports deliverability, but it does not guarantee that a message will reach the inbox; providers also consider reputation, recipient behavior, and other signals.

SPF identifies the servers and services permitted to send mail for a domain. DKIM adds a digital signature that receiving systems can check against a public key published in DNS. Together, these records help verify parts of a message’s sending path and content. Each email platform that sends on your behalf may require specific configuration, so keep an accurate inventory of vendors and mail streams.

DMARC builds on SPF and DKIM by checking whether the authenticated domain aligns with the domain recipients see in the From address. It also lets a domain owner publish a policy for messages that fail those checks and request reports about authentication results. Teams often review reports while monitoring before moving to a stricter policy, so legitimate senders are not accidentally affected.

Common problems include publishing more than one SPF record for a domain, leaving out a service that sends on your behalf, or changing keys and DNS records without checking every sending stream. Before changing a policy, identify marketing, transactional, customer support, and other mail sources. Coordinate DNS changes with the people responsible for your domain and verify the results after updates.

Authentication works best as part of ongoing deliverability monitoring. Inbox Rev helps teams review sender configuration alongside inbox placement and reputation, so authentication results can be understood in the context of the mail streams they support.