Troubleshooting

DKIM not signing emails? How to fix it

If your email is failing DKIM checks, it usually means one of several things is wrong. Here is how to diagnose and fix it.

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What does "DKIM not signing" mean?

When a receiving server says your email "failed DKIM," it means one of these:

Your DKIM record is missing from DNS
Your DKIM selector does not match the one your email provider uses
Your DKIM key is too weak (less than 1024 bits)
Your DKIM domain does not align with your "From" domain

Step 1: Check your DKIM record

Run this command to check your DKIM record:

dig +short TXT google._domainkey.yourdomain.com

Replace google with your actual DKIM selector. If the command returns nothing, your DKIM record is missing.

Step 2: Verify the selector

Make sure the DKIM selector in your DNS matches the one your email provider uses. For example, if you use Google Workspace, the selector is usually google. If you use Microsoft 365, it is usually selector1 or selector2.

If they do not match, DKIM will fail.

Step 3: Check the key strength

Modern DKIM keys should be at least 1024 bits. If your key is 512 bits, many receiving servers will reject it.

Run the free InboxProof DKIM checker to verify your key strength.

Step 4: Check domain alignment

For DKIM to pass, the domain in your DKIM signature must align with the domain in your "From" header. If they do not match, DKIM will fail.

For example, if your "From" domain is yourdomain.com, your DKIM signature must also be for yourdomain.com (or a subdomain of it).

Step 5: Verify the fix

After making the changes, run the free InboxProof DKIM checker to confirm your DKIM record is configured correctly. The checker verifies:

DKIM record exists and is valid
Key strength is at least 1024 bits
Domain alignment with your "From" domain

Fix your DKIM issue

Run the free DKIM checker and see if your DKIM record is configured correctly.

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