Debugging Inbound Emails Failing DKIM Checks on Microsoft Exchange Server 2019 with Windows Server 2022

Debugging Inbound Emails Failing DKIM Checks on Microsoft Exchange Server 2019 (Windows Server 2022)

DomainKeys Identified Mail (DKIM) is an email authentication method that helps protect your organization from spam and phishing attacks. When inbound emails fail DKIM checks, it can be a sign of a compromised email account or a misconfiguration in your email server. In this article, we will cover the key concepts and steps to debug inbound emails failing DKIM checks on Microsoft Exchange Server 2019 running on Windows Server 2022.

Understanding DKIM

DKIM is a method of authenticating emails that uses public key cryptography to verify the sender's domain. When an email is sent, the sender's email server adds a digital signature to the email's header. The recipient's email server can then use the sender's public key to verify the signature and confirm that the email was not tampered with during transmission.

Checking DKIM Signatures

To check DKIM signatures, you can use the following PowerShell command:

This command retrieves all email messages with the subject "Test Email" sent in the last 7 days and filters the results to show only messages with a DKIM signing status of "Fail".

Debugging Failed DKIM Signatures

If you find that inbound emails are failing DKIM checks, there are several possible causes:

• The sender's email server is not properly configured for DKIM
• The sender's DKIM key has expired
• The sender's DKIM key has been revoked
• The sender's DKIM key has been compromised
• The recipient's email server is not properly configured to validate DKIM signatures

To debug failed DKIM signatures, you can use the following steps:

1. Check the sender's DKIM record: Use a DNS lookup tool to check the sender's DKIM record and ensure that it matches the sender's public key.
2. Check the sender's DKIM key: Ensure that the sender's DKIM key is still valid and has not been revoked or compromised.
3. Check the recipient's DKIM configuration: Ensure that the recipient's email server is properly configured to validate DKIM signatures.
4. Enable pipeline tracing: Enable pipeline tracing in Microsoft Exchange Server 2019 to get more information about the email message and the DKIM validation process.

Enabling Pipeline Tracing

To enable pipeline tracing in Microsoft Exchange Server 2019, you can use the following PowerShell command:

This command enables pipeline tracing for all email messages processed by the Exchange Server.

Debugging inbound emails failing DKIM checks on Microsoft Exchange Server 2019 running on Windows Server 2022 involves checking the sender's DKIM record and key, ensuring that the recipient's email server is properly configured to validate DKIM signatures, and enabling pipeline tracing to get more information about the email message and the DKIM validation process.

References

• Use DKIM to validate incoming email
• Use DKIM to validate outgoing email
• Use message trace to trace email messages
• Use pipeline tracing to troubleshoot message delivery issues