DKIM: Definition and Use Cases
DKIM (DomainKeys Identified Mail) is a cryptographic signature added to email by the sender. The public key is published in DNS (selector._domainkey.example.com); the private key signs the message body. The recipient verifies the signature, guaranteeing the message was not modified in transit and truly came from the claimed domain.
What is DKIM
DKIM (DomainKeys Identified Mail) is a cryptographic signature added to email by the sender. The public key is published in DNS (selector._domainkey.example.com); the private key signs the message body. The recipient verifies the signature, guaranteeing the message was not modified in transit and truly came from the claimed domain.
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How it works
Enter domain and selector
Fetch DKIM TXT record
Validate public key
What is DKIM?
DKIM (DomainKeys Identified Mail) is a mechanism to digitally sign email with a key stored in DNS. This allows recipients to verify that the email was genuinely sent from the specified domain.
Selector-based Check
Specify domain and DKIM selector — get the public key and its parameters.
Key Analysis
RSA/Ed25519 key length, hash algorithm, flags, and validity period.
Recommendations
If key < 2048 bits — we issue a warning and key rotation instructions.
Instant Result
Direct DNS query in seconds — no waiting for TTL.
Who uses this
Email marketers
pre-send verification
Sysadmins
mail server setup
Security
phishing protection audit
Developers
email deliverability debug
Common Mistakes
Best Practices
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DKIM check history and DNS monitoring for domain record changes.
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Frequently Asked Questions
Do I need DKIM?
If you work with web infrastructure or APIs, almost certainly yes. See the article above for specific use cases.