What Is a DKIM Selector?
Understanding DKIM selectors and key identification
Table of Contents
What Is a DKIM Selector?
A DKIM selector is an identifier used to distinguish different DKIM key pairs for the same domain. DKIM selectors enable domains to use multiple DKIM keys simultaneously, allowing key rotation, different keys for different services, and key management flexibility.
DKIM selectors are used in DKIM signatures (s=selector) and DNS record lookups (selector._domainkey.example.com). DKIM selectors can be any string (e.g., 'default', 'google', '2024'), allowing domains to organize and manage multiple DKIM keys.
DKIM selectors are essential for DKIM - without selectors, domains cannot use multiple keys or rotate keys. Check DKIM selectors using our DKIM lookup tool. Learn more about DKIM.
DKIM Selector Purpose
Key Identification
DKIM selectors identify which DKIM key pair was used to sign an email, enabling receiving servers to find the correct public key for verification.
Multiple Keys
DKIM selectors enable domains to use multiple DKIM keys simultaneously, allowing different keys for different services or mail servers.
Key Rotation
DKIM selectors enable key rotation by allowing domains to publish new keys with new selectors while keeping old keys active during transition.
Key Management
DKIM selectors provide key management flexibility, allowing domains to organize and manage multiple DKIM keys efficiently.
Service Separation
DKIM selectors enable different services or mail servers to use different DKIM keys, providing service-level key management.
DKIM Selector Format
Selector in Signature
DKIM selectors appear in DKIM signatures: DKIM-Signature: ... s=selector; ...
DNS Record Location
DKIM public keys are published at: selector._domainkey.example.com
Selector Examples
default- Default selectorgoogle- Google-specific selector2024- Year-based selectormail- Service-based selector
Selector Requirements
DKIM selectors can be any string, but should be descriptive and consistent for key management.
Selector Lookup
Receiving servers use selector from DKIM signature to lookup public key: selector._domainkey.example.com
Multiple Selectors
Why Use Multiple Selectors?
Multiple selectors enable: key rotation (old and new keys active simultaneously), service separation (different keys for different services), and key management (organizing keys by purpose or date).
Key Rotation Example
During key rotation: old key uses selector '2023', new key uses selector '2024', both keys are active during transition, and old key is removed after transition.
Service Separation Example
Different services use different selectors: marketing emails use selector 'marketing', transactional emails use selector 'transactional', and each service has its own DKIM key.
Selector Management
Manage multiple selectors by: documenting selector purposes, tracking selector usage, and removing unused selectors.
Best Practices
Use descriptive selectors, maintain selector documentation, and clean up unused selectors regularly.
Checking DKIM Selectors
1. DKIM Lookup Tools
Use our DKIM lookup tool to check DKIM selectors and verify DKIM key configuration.
2. Email Headers
Check DKIM signatures in email headers to identify which selectors are being used: DKIM-Signature: ... s=selector; ...
3. DNS Lookup
Query DNS for DKIM records: dig TXT selector._domainkey.example.com
4. Verification
Verify DKIM selectors are configured correctly, DNS records are published, and selectors match DKIM signatures in emails.
5. Email Authentication
Use our email authentication checker to verify DKIM authentication is working correctly with selectors.
