Three unfamiliar-looking DNS records — SPF, DKIM, and DMARC — quietly determine whether email sent from your domain lands in an inbox or gets filtered straight to spam, and increasingly, whether it gets accepted by major email providers at all. Understanding what each one actually does removes most of the mystery around deliverability problems.
What Each Record Actually Does
SPF (Sender Policy Framework) is a DNS record listing which mail servers are authorized to send email on behalf of your domain. When an email arrives claiming to be from your domain, the receiving server checks SPF to confirm it actually came from an authorized source — without it, anyone could send email pretending to be from your domain with no verification at all.
DKIM (DomainKeys Identified Mail) adds a digital signature to outgoing email, verifying the message wasn't altered in transit and genuinely originated from your domain's authorized sending system. It works alongside SPF as a second, complementary layer of authentication.
DMARC (Domain-based Message Authentication, Reporting, and Conformance) builds on top of both, telling receiving mail servers what to do when a message fails SPF or DKIM checks (reject it, quarantine it, or just monitor and report), and provides reporting back to you about how your domain's email is being used and authenticated across the internet.
Why This Matters More Than It Used To
Major email providers have tightened requirements around these records significantly, particularly for anyone sending email at any real volume. Missing or misconfigured authentication is now one of the most common reasons legitimate email ends up in spam, or gets rejected outright, rather than being a minor best practice that only mattered for large senders.
A Simple Framework
- Confirm all three records are actually set up correctly for your domain — a surprising number of domains have none of them configured, or have them set up incorrectly
- Start with SPF and DKIM as the foundation, since DMARC depends on both being correctly configured to function meaningfully
- Begin DMARC with a monitoring-only policy before moving to a stricter enforcement policy, so you can see how your legitimate email is authenticating before risking it being rejected
- Check these records periodically, especially after changing email providers or adding new sending services, since a change on one end without updating these records is a common cause of sudden deliverability problems
> Tip: If you use multiple services to send email from your domain (a website contact form, a marketing platform, a support tool, and a personal mailbox, for example), each one needs to be properly included in your SPF and DKIM setup. A common deliverability problem is adding a new sending service without updating these records to authorize it.
Common Mistakes
- Never setting up these records at all, leaving email authentication entirely absent
- Setting up SPF but forgetting to update it when adding a new email-sending service
- Jumping straight to a strict DMARC enforcement policy without first confirming legitimate email passes authentication correctly
- Assuming deliverability problems are always about content or reputation, without checking whether basic authentication is even correctly configured
If you're unsure whether your current setup handles this correctly, most quality hosting providers, including KnownHost, offer support in properly configuring these DNS records alongside your email hosting setup.
These three records are entirely invisible to anyone reading an email, and entirely decisive in whether that email ever reaches them at all. Getting them right is one of the highest-leverage, lowest-effort fixes available for anyone struggling with email deliverability.