Frequently asked questions
What is a DKIM record?
DKIM (DomainKeys Identified Mail) adds a digital signature to outgoing emails. The sending server signs each message with a private key, and the receiving server looks up the corresponding public key in DNS to verify the signature. This confirms the message was authorized by the domain owner and was not altered in transit.
What is a DKIM selector?
A selector is a label used to locate the public key in DNS. The full lookup is selector._domainkey.yourdomain.com. Different email providers use different selectors — for example, Google Workspace uses google, Microsoft 365 uses selector1 and selector2, and Mailchimp uses k1.
Why does key length matter?
RSA keys shorter than 2048 bits are considered weak and may be vulnerable to attacks. NIST recommends a minimum of 2048-bit RSA keys. If your DKIM key is 1024 bits or shorter, contact your email provider to rotate to a stronger key.
What if no DKIM record is found?
If we cannot find a DKIM record, it may mean DKIM is not configured, or your provider uses a custom selector we did not probe. Try entering your selector manually — your email provider can tell you which selector to use. Check the DKIM-Signature header in a sent email to find the s= value.
Can I have multiple DKIM selectors?
Yes. Multiple selectors are common and expected. Different email services (your primary email, marketing platform, transactional email, etc.) each use their own selector. This is the correct way to authorize multiple senders — unlike SPF, there is no lookup limit for DKIM.
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