DKIM Checker
Looks up the public DKIM key for a domain and validates every tag in the record. Leave the selector empty and the tool scans the selectors used by the major mail providers for you.
The domain that signs the mail, not the sending server.
Leave empty to scan the common provider selectors automatically.
How DKIM and Selectors Work
A DKIM key lives in a TXT record at {selector}._domainkey.{domain}. The sending server stamps each message with a signature and names the selector it used, so a receiver knows which key to fetch. That is why a domain can publish several keys at once — one per provider that sends on its behalf.
- v
- Version. When present it must be exactly DKIM1.
- k
- Key type: rsa (almost always) or ed25519.
- p
- The public key itself, base64 encoded. An empty p means the key has been revoked.
- h
- Hash algorithms the key may be used with. sha256 is expected; sha1 alone is obsolete.
- t
- Flags. t=y puts the key in testing mode, which tells receivers to ignore signature failures. t=s stops the key covering subdomains.
- s
- Service types the key applies to. Defaults to * (all).
- n
- A free-text note for administrators. Ignored by receivers.
DKIM on its own only proves a message was signed. Pair it with SPF and a DMARC policy of reject before your domain is actually protected from spoofing.
How to use it
- Enter Domain or IP Enter the domain name, IP address, or URL into the Dkim Checker to start the lookup or analysis.
- Run the Check Click the check button to query the relevant databases. Results are retrieved and displayed in seconds.
- Analyze the Results Review the detailed results including status, records, and diagnostics to troubleshoot or verify your query.
Tip Compare results from the Dkim Checker with your hosting provider's dashboard to spot discrepancies early.
What is DKIM and Why It Matters
DomainKeys Identified Mail (DKIM) is an email authentication method designed to detect forged sender addresses in emails, a common tactic used in phishing and spam. DKIM works by adding a digital signature to the headers of an email message. This signature is generated using a private cryptographic key held by the sending domain.
When an email is received, the recipient’s mail server uses the public key published in the sender’s DNS records to verify the signature. If the signature matches, it confirms that the email was indeed sent by the domain it claims to be from and that the message has not been altered in transit.
Why is this important? Without DKIM, it’s easier for attackers to impersonate legitimate domains, tricking recipients into opening malicious emails. DKIM helps improve email deliverability and protects recipients from spoofed emails.
Common use cases include:
- Businesses ensuring their marketing or transactional emails are trusted by recipients and spam filters.
- Email service providers verifying incoming messages to reduce spam and phishing.
- Domain owners validating their email infrastructure to comply with security best practices.
Understanding DKIM
DomainKeys Identified Mail (DKIM) is a method used to authenticate email messages by attaching a digital signature to the email headers. This signature is created using a private key and verified by recipients using a public key published in DNS. The purpose is to confirm that the email was sent by an authorized sender and that its content has not been tampered with during transmission.
DKIM plays a crucial role in preventing email spoofing and phishing attacks, which rely on forging sender addresses. By verifying the signature, mail servers can trust the origin of the message and improve deliverability.
When to Use a DKIM Checker
- Before sending large volumes of email, to ensure your DKIM signatures are valid and correctly configured.
- When setting up or migrating email services to verify that DKIM records are properly published and aligned.
- To diagnose email delivery problems related to authentication failures.
- As part of ongoing email security audits alongside SPF and DMARC checks.
Common Mistakes to Avoid
- Incorrectly publishing the DKIM public key in DNS, which leads to failed verification.
- Using inconsistent selector names between DNS and email headers.
- Relying solely on DKIM without implementing SPF and DMARC.
- Neglecting to rotate DKIM keys regularly, which can weaken security over time.
Using a DKIM checker helps identify these issues by verifying the presence and correctness of DKIM signatures and DNS records. This ensures your emails are authenticated properly, reducing the chance of being marked as spam or rejected.
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