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Postmark DKIM Signature Invalid

The DKIM signature is incorrect or not matching the domain's DNS records.

Understanding Postmark and Its Purpose

Postmark is a reliable and fast email delivery service designed for developers. It provides APIs for sending transactional emails, ensuring that your emails reach the inbox quickly and securely. Postmark is particularly known for its excellent deliverability and detailed analytics, making it a preferred choice for many production applications.

Identifying the Symptom: DKIM Signature Invalid

When using Postmark, you might encounter an error indicating that the DKIM Signature is Invalid. This error typically appears in email headers or logs and can prevent your emails from being delivered successfully.

What is DKIM?

DKIM (DomainKeys Identified Mail) is an email authentication method that allows the receiver to check that an email was indeed sent and authorized by the owner of that domain. It helps in preventing email spoofing.

Explaining the Issue: DKIM Signature Invalid

The error DKIM Signature Invalid suggests that the DKIM signature attached to your outgoing emails does not match the expected signature based on your domain's DNS records. This mismatch can occur due to incorrect DKIM settings or outdated DNS records.

Common Causes

  • Incorrect DKIM key in DNS records.
  • Changes in DNS records not propagated.
  • Misconfigured email sending settings.

Steps to Fix the DKIM Signature Invalid Issue

Resolving this issue involves verifying and updating your DKIM settings. Follow these steps:

Step 1: Verify Current DKIM Settings

Check your current DKIM settings in your DNS records. You can use tools like MXToolbox DKIM Lookup to verify if your DKIM record is correctly set up.

Step 2: Update DKIM Record

If the DKIM record is incorrect, update it in your DNS provider's dashboard. Ensure that the DKIM key provided by Postmark is correctly entered. Refer to Postmark's DKIM setup guide for detailed instructions.

Step 3: Propagate DNS Changes

After updating the DKIM record, allow some time for DNS changes to propagate. This can take anywhere from a few minutes to 48 hours, depending on your DNS provider.

Step 4: Test Email Delivery

Once the DNS changes have propagated, send a test email to ensure that the DKIM signature is now valid. You can use email testing tools like Mail Tester to verify the DKIM signature.

Conclusion

By following these steps, you can resolve the DKIM Signature Invalid issue and ensure that your emails are authenticated correctly, improving deliverability and security. For further assistance, consult the Postmark Support page.

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