🔐 DKIM, SPF and DMARC — what does each one actually do?
If you're sending email from your own domain, these three DNS mechanisms matter:
SPF tells receiving servers which mail servers are allowed to send on behalf of your domain.
DKIM adds a cryptographic signature to each message so the receiver can verify that the email wasn't modified in transit.
DMARC tells receiving servers what to do when SPF or DKIM checks fail and gives domain owners visibility into authentication problems.
A simple way to think about it:
SPF → Who can send?
DKIM → Is the message authentic?
DMARC → What happens if verification fails?
Having all three configured correctly is one of the foundations of good email deliverability.
We automate this setup in Postwing, but the concepts apply regardless of which email provider you use.
More on email infrastructure:
https://postwing.app/docs
August 10, 2026 2
