Definition
DKIM (DomainKeys Identified Mail) attaches a digital signature to every email you send. Receiving servers look up your public DKIM key in DNS, decrypt the signature, and verify that the email has not been modified since it was signed.
Setup Process
- Your ESP generates a public-private DKIM key pair
- You publish the public key as a DNS TXT record at
[selector]._domainkey.yourdomain.com - Your ESP signs outgoing mail with the private key
- Receiving servers look up your public key and verify the signature
Record Format
v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb4...long-public-key...
Key Management
- Selector: A label that allows multiple DKIM keys (useful for rotating keys without interruption)
- Key length: 1024-bit keys are common but 2048-bit is more secure
- Rotation: Regenerate keys every 6-12 months
- Multiple selectors: Use different selectors for different sending streams or ESPs
Common Mistakes
Publishing an incorrectly formatted key, using a key shorter than 1024 bits, and failing to rotate keys periodically.
Related Glossary Terms
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BIMI
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Bounce Rate Threshold
A bounce rate threshold is the percentage of hard or soft bounces at which email platforms and ISPs begin to penalise sender reputation, typically around 2-5%.
Bounce Rate
Email bounce rate is the percentage of emails that were rejected by the receiving server before reaching the recipient. It is a key indicator of list health and data quality.
Email Deliverability
Email deliverability is the ability to land in the recipient's inbox rather than the spam folder. It depends on sender reputation, authentication, list quality, and content practices.
DKIM (DomainKeys Identified Mail)
DKIM (DomainKeys Identified Mail) is an email authentication method that uses digital signatures to verify that an email was not tampered with during transit and comes from a authorised domain.