DKIM Failures: The Hidden Culprit Behind Email Deliverability Issues
Imagine sending an important email, but instead of landing in your recipient’s inbox, it gets marked as "unauthenticated" or worse—sent to spam. If you've ever faced this, there's a high chance your DKIM (DomainKeys Identified Mail) authentication is broken.
But don’t worry! DKIM failures are common, and in this guide, we’ll help you understand:
✅ Why DKIM fails
✅ How to diagnose the issue
✅ How to regenerate and configure a new DKIM key
Why Does DKIM Fail? Common Reasons & Fixes
1️⃣ Expired or Rotated DKIM Keys
🔹 DKIM keys expire or get rotated automatically by some email providers.
💡 Fix: Check if your DKIM selector has changed and update your DNS records.
2️⃣ Incorrect DKIM Record in DNS
🔹 A simple typo in your TXT record can cause authentication failures.
💡 Fix: Use a DNS lookup tool to verify your DKIM record format.
3️⃣ DKIM Key Too Long (2048-bit Key Issues)
🔹 Some DNS providers don’t support 2048-bit DKIM keys, leading to truncation issues.
💡 Fix: Split the key into two parts and update your DNS accordingly.
4️⃣ Multiple DKIM Records Causing Conflicts
🔹 If multiple DKIM TXT records exist for the same selector, it confuses mail servers.
💡 Fix: Keep only one valid DKIM key per selector.
5️⃣ Email Sent from an Unauthorized Source
🔹 If a third-party service sends emails on your behalf but doesn’t have DKIM configured, it will fail.
💡 Fix: Ensure all email senders (Gmail, Outlook, SMTP relays) have DKIM signing enabled.
How to Regenerate a New DKIM Key & Update DNS
Step 1️⃣: Generate a new DKIM key from your email provider
For Google Workspace:
bashCopyEditopenssl genrsa -out dkim_private.pem 2048 openssl rsa -in dkim_private.pem -pubout -out dkim_public.pem
For Microsoft 365:
🔹 Go to Admin Center → Exchange → DKIM Settings → Enable DKIM
For cPanel:
🔹 Navigate to Email Deliverability → DKIM → Generate New Key
Step 2️⃣: Update the DKIM TXT record in your DNS
🔹 Add this to your DNS (replace yourdomain.com and selector accordingly):
txtCopyEditselector._domainkey.yourdomain.com TXT "v=DKIM1; k=rsa; p=MIGfMA..."
💡 Pro Tip: Some DNS providers need the key split into chunks for 2048-bit support.
Step 3️⃣: Verify DKIM is Working
After updating the DNS, verify your DKIM setup using:
✅ YourDMARC’s DKIM Lookup Tool heck it in real-time!)
Final Thoughts: Lock in Email Security with DKIM!
If your DKIM is failing, don’t panic. A quick regeneration and DNS update can get your email security back on track. 🔐
Still facing issues? YourDMARC’s email security tools can help you analyze, troubleshoot, and monitor your domain’s DKIM health in real-time.
🔹 Check your DKIM setup now! 🚀