SPF checks where an email came from. DKIM checks whether it arrived unchanged. They solve different problems, and DKIM only carries real weight when it’s paired with a valid SPF record too — the two are usually diagnosed together.

What DKIM Actually Does

DKIM (DomainKeys Identified Mail) attaches a digital signature to every outgoing email, generated using a private key that only your sending platform holds. The receiving mail server checks that signature against a public key published in your domain’s DNS. If the message was altered in transit — even a single character — the signature fails to verify, and the email can be flagged or rejected.

Unlike SPF, which is one record covering your whole domain, DKIM is set up per sending platform. Your storefront’s transactional emails, your Klaviyo campaigns, and your Google Workspace mail may each need their own DKIM record, each with a different “selector” name.

Why DKIM Breaks Most Often

Mismatched or Missing Selectors

A DKIM record is published at a specific hostname that includes a selector, something like selector1._domainkey.yourdomain.com. If the selector in DNS doesn’t exactly match what the sending platform expects, the signature check fails silently — there’s no error message, mail simply stops being signed correctly.

Alignment Issues With SPF and DMARC

DMARC requires DKIM (or SPF) to “align” with the domain in the visible From address. A DKIM signature can technically pass its own check while still failing DMARC alignment, if the signing domain doesn’t match closely enough. This is one of the most common places we see a store’s authentication look fine in isolation but fail once DMARC is added — DMARC alignment depends on this [link once published].

Forgetting to Add DKIM for a New Platform

SPF gets attention because a missing SPF include is easy to notice. DKIM is quieter — a newly added sending platform can go weeks without a correctly published DKIM record before anyone notices deliverability quietly declining.

Why This Isn’t a Quick DNS Edit

Publishing a DKIM record correctly requires matching the exact selector and key value your sending platform generated — not a generic template copied from a forum post. A mismatched or malformed DKIM record doesn’t just fail to help; it can create a false sense of security where a domain looks authenticated but isn’t actually passing checks where it matters.

Signs DKIM May Be the Issue

• SPF checks out fine, but deliverability is still inconsistent
• A new email platform or marketing tool was added without a full DNS review afterward
• DMARC reports show SPF passing but DKIM failing, or vice versa
• Multiple sending platforms are in use, each potentially needing its own DKIM setup

What an Alneeko Email Deliverability Audit Covers

• Verification of DKIM signatures for every platform sending mail as your domain
• Selector and alignment checks against your SPF and DMARC setup
• A plain-language report on what’s signed correctly and what isn’t
• Correct DKIM publication as part of a coordinated fix across all three records

Get Your DKIM Setup Checked

DKIM problems are easy to miss because they rarely produce an obvious error. If you’ve added a new sending platform recently, or you’re not certain your DKIM records are correctly aligned, it’s worth a proper check. Book an Email Deliverability Audit with Alneeko Technologies, or see the full deliverability guide for the complete picture across SPF, DKIM, DMARC, and compliance.