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Email Marketing Glossary.

Clear, no-fluff definitions of every email marketing term that matters—from open rates to double opt-in. 

 

DKIM

DKIM (DomainKeys Identified Mail) is an authentication method that attaches a cryptographic signature to your emails, letting receiving servers verify they genuinely came from your domain and weren't altered.

Also known as: DomainKeys Identified Mail

DKIM is the digital signature of email authentication. It proves two things at once: that the message really came from your domain, and that no one tampered with it in transit.

How does DKIM work?

Your sending platform signs each email with a private key. A matching public key lives in your DNS. Receiving servers use it to verify the signature — if it checks out, the message is authentic.

Why does DKIM matter?

DKIM strengthens trust with mailbox providers and is required, alongside SPF and DMARC, to meet the sender requirements Gmail and Yahoo enforce. Missing DKIM hurts deliverability.

DKIM and the other protocols

SPF says which servers can send; DKIM proves the message is genuine and intact; DMARC ties both together and sets the policy for failures.

Related terms

Email Deliverability Sender Reputation SPF DMARC Hard Bounce

Related reading from Drip

Ecommerce Email Deliverability: 9 Ways to Reach the Inbox Setting Up Custom Sending Domains (Help Center)

Frequently asked questions

What does DKIM stand for?
DKIM stands for DomainKeys Identified Mail. It's an authentication protocol that adds a cryptographic signature to your emails so receiving servers can verify they're authentic and unaltered.
How does DKIM work?
Your email platform signs each message with a private key, and a matching public key is published in your DNS. Receiving servers check the signature against the public key to confirm the email genuinely came from your domain and wasn't tampered with.
Why is DKIM important?
DKIM builds trust with mailbox providers and is required — alongside SPF and DMARC — to meet the sender rules enforced by Gmail, Yahoo, and Microsoft. Without it, deliverability suffers.
What's the difference between SPF and DKIM?
SPF authorizes which servers may send on your behalf, while DKIM cryptographically signs each message to prove it's authentic and unchanged. They address different risks and work best together, enforced by DMARC.
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