DKIM

DomainKeys Identified Mail - an email authentication method adding a digital signature.

1 min readLast updated Apr 2026

Reviewed by Golden Digital·Operator-reviewed ecommerce reference

Quick Reference

CategoryEmail Marketing & Klaviyo

Related Terms2

DomainKeys Identified Mail - an email authentication method adding a digital signature.

Why It Matters

DKIM adds a cryptographic signature to your emails proving they haven't been tampered with in transit. This builds trust with receiving servers and is essential for DMARC alignment. Gmail and Yahoo now require DKIM authentication for bulk senders.

Practical Example

Scenario

A CPG brand notices their emails show 'mailed-by: klaviyo.com' instead of their domain, and some corporate servers reject them.

Calculation

Without DKIM signing on their domain, emails appear to come from Klaviyo, not their brand

Result

After setting up custom DKIM (adding DNS records from Klaviyo), emails show their domain and pass authentication checks. Corporate server delivery improves.

Pro Tips

1Set up custom DKIM (branded sending domain) through your ESP—don't use their default shared signing
2Use 2048-bit keys for stronger security (1024-bit is minimum, increasingly deprecated)
3Rotate DKIM keys periodically (annually) as a security best practice
4Verify DKIM is passing by checking email headers in received messages

Common Mistakes to Avoid

Using default ESP signing instead of setting up custom DKIM on your domain

Incorrectly copying DNS records (extra spaces, missing characters cause failures)

Not verifying DKIM is actually passing after setup

Frequently asked questions

SPF validates the sending server is authorized. DKIM validates the message content hasn't been altered. Together with DMARC, they cover who sent the email, whether it changed, and what to do when a check fails.

Your ESP provides DKIM records (CNAME or TXT entries) to add to your DNS. After adding them, verify in your ESP and test with MXToolbox DKIM Lookup or by checking email headers.

Put it to work

Related Terms

SPF

Sender Policy Framework - a DNS-based email authentication protocol.

DMARC

A policy protocol instructing servers how to handle emails that fail SPF or DKIM checks.

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