How to Fix DKIM Verification Failures & Selector Mismatches
⚠️ Technical Alert
Symptoms Checklist
If you observe any of the following symptoms, your site or setup is affected by this issue:
- Email headers showing 'dkim=fail' or 'dkim=invalid'
- DKIM signature verification failed warnings in diagnostic tests
- Emails bouncing due to DKIM body hash mismatch errors
- Incorrect selector key name settings causing DNS lookups to fail
Why This Happens
DKIM cryptographically signs outgoing emails. If receiving servers cannot find the matching public key in your DNS records, or if the signature is formatted incorrectly, the DKIM check fails.
Common Underlying Causes
- Incorrect DNS TXT Value: Copy-pasting the DKIM key string from your provider with extra spaces or missing characters.
- Selector Mismatches: Sending mail with a selector prefix (e.g. google._domainkey) that does not match the DNS record.
- DNS Character Limits: Old DNS providers truncating long 2048-bit DKIM keys.
DIY Quick Fix Steps
Here is what you can check or execute immediately to troubleshoot the issue:
- Send a test email to a Gmail address and select 'Show original' in the menu.
- Check the 'DKIM-Signature' header and locate the selector ('s=') tag.
- Perform a DNS query for '[selector]._domainkey.yourdomain.com' and verify it returns your public key.
- If missing or mismatched, generate a new key inside your email hosting console.
⚠️ Caution: Changing DNS, server logs, or WordPress databases incorrectly can cause site downtime. If you're not comfortable, skip these steps and hire assistance.
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