You can write the best email in the world but if mailbox providers can’t prove it really came from you, they’ll treat it like junk.
That’s where DKIM comes in.
DKIM (DomainKeys Identified Mail) is a digital signature system for email. It’s how your messages prove they haven’t been tampered with on their journey from your outbox to someone else’s inbox.
Think of it as a wax seal for email: if it arrives unbroken, it’s authentic.
How DKIM Works
Every domain that sends email under DKIM has two cryptographic keys:
- A private key, stored safely on your mail server.
- A public key, published in your DNS.
When you send an email, your server adds a DKIM signature — a unique block of encrypted text in the message header.
When the recipient’s mail server receives it, it looks up your public key in DNS and checks the match.
If everything lines up, the message passes DKIM and is marked as authentic.
If it doesn’t, something’s wrong — the email was altered, forged, or the record’s broken.
What a DKIM Record Looks Like
Your DKIM record lives in DNS and usually looks something like this:
v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBA…Each sending platform (like your CRM, ATS, or newsletter tool) uses its own selector (basically a label that identifies which DKIM key to use).
You can view or verify yours using any DNS lookup tool or within Quinset’s deliverability dashboard if you’re a client.
Why You Need DKIM
- Prevents message tampering
The digital signature proves the message hasn’t been edited mid-flight. If someone tries, it fails DKIM and gets rejected. - Stops domain spoofing
Attackers can’t fake your private key. Without it, their forged messages won’t pass DKIM. - Reduces spam risk
A valid DKIM signature signals to mailbox providers that you’re a verified sender, improving inbox placement. - Builds trust and deliverability
Every successful DKIM check adds to your domain reputation, the quiet metric that decides where your emails land.
How DKIM Prevents Spoofing
DKIM works like a fingerprint.
Even if someone copies your logo and “From” address, they can’t copy your private key.
That means mailbox providers can instantly spot a fake and bin it before it reaches anyone’s inbox.
Limitations of DKIM
DKIM is essential, but not everything:
- It authenticates the domain, not the individual user. If someone has your login, they can still send.
- Misconfigured DNS records can cause failures, especially if you’ve switched CRMs or mail servers.
- It doesn’t block spam on its own — DKIM just proves the sender’s real, not that the message is welcome.
That’s why DKIM works best paired with DMARC.
Pairing DKIM with DMARC
DMARC uses your DKIM and SPF results to decide what to do with unauthenticated messages. Monitor, quarantine, or reject them.
Together they:
- Prevent spoofing and domain abuse
- Improve inbox placement
- Give you visibility through daily DMARC reports
In short: DKIM tells the truth about who sent the message.
DMARC enforces what happens if that truth doesn’t check out.
Reality Check
DKIM is one of those “set it once, but check it often” records.
Every time you add a new sending platform (newsletter tool, CRM, recruitment system) you’ll need to add its DKIM record too.
Skip that, and half your mail might fail silently.
Next Step
If you’re not sure whether your DKIM’s live or working, run a DKIM lookup or send yourself a test through your own CRM.
If the results look odd, or you’re juggling multiple senders, we can review your setup and align SPF, DKIM, and DMARC so everything signs cleanly.
Book a 30-minute call and we’ll help you check your domain health before your next send.
