What does “Invalid DKIM signature" mean?

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What does “Invalid DKIM signature" mean?

Introduction: What is DKIM, and what are its benefits?

DomainKeys Identified Mail, or DKIM, is a technology used to verify the identity of email senders and recipients. DKIM works by attaching a cryptographic signature to each email message sent. The recipient's email server can verify this signature to ensure that the purported sender sent the message.

The main benefit of using DKIM is that it can help to reduce spam and malware. By verifying the sender's identity, DKIM helps to ensure that only legitimate messages are delivered to recipients' inboxes. This can help reduce the amount of spam and malware that recipients receive, improving their overall experience when using email.

DKIM, coupled with DMARC, also helps prevent spoofing attacks, which anyone can do by sending forged messages with the correct sender address.

How does DKIM work?

DomainKeys Identified Mail (DKIM) is an email authentication system used to identify email senders. DKIM allows senders to attach a digital signature to their messages, which verifies the message was sent by them and not spoofed. When a message is received with a valid DKIM signature, the recipient can be confident that the message is from the claimed sender and has not been modified in transit.

To use DKIM, the sending domain must first be registered with authorized signing authority. The signing authority will generate a public-private key pair and provide the public key to the domain owner. The private key is kept secret by the signing authority. When sending an email, the sender encrypts the message with their private key and includes the encrypted message and the corresponding public key in the header of the email. When a recipient receives the email, the recipient can validate the DKIM signature by using the sender's public key to decrypt the message. If this is successful, the message has been validated and can be trusted as authentic.

DKIM public key entries are present either as TXT or CNAME record entries in the DNS for a domain.

What is an invalid DKIM signature?

An invalid DKIM signature results from an email authentication verification that is used to protect against spam and email spoofing. DKIM uses a public-private key pair to create a signature attached to all outgoing emails. The recipient's email server can then use the public key to verify that anyone did not alter the message in transit.

A valid DKIM signature means that the message has not been tampered with and that the email came from the authorized sender. An invalid DKIM signature means either the message was tampered with or originated from an unauthorized source.

DKIM is used to determine whether someone altered email messages in transit. Suppose a message has an invalid DKIM signature. In that case, the recipient's email server will not be able to verify that it came from the sender and is therefore not trustworthy.

How can you tell if your DKIM signature is invalid?

If DKIM key or hash is not present:

There are a few different ways to tell if your DKIM signature is invalid. The first way is to check the DKIM record in the DNS. You can do this with a tool like MXToolbox or dkimvalidator. If the DKIM record doesn't exist, your DKIM signature is invalid.

Another way to check for an invalid DKIM signature is by checking the message headers. You can do this with a tool like Message Header Analyzer. If the DKIM-Signature header field doesn't exist, your DKIM signature is invalid.

The final way to check for an invalid DKIM signature is by checking the message body. You can do this with a tool like DMARC Analyzer. If there's no evidence of a DKIM signature in the message body, your DKIM signature is invalid.

If there is a mismatch between the DKIM hash in the domain header and the Domain's DKIM key:

DomainKeys Identified Mail (DKIM) is an email authentication system used to verify the sender of an email. A DKIM signature is created by adding a header to an email message, then cryptographically signed using a private key. The signature is verified by the recipient using the sender's public key.

If there is a mismatch between the DKIM hash in the domain header and the Domain's DKIM key, either the message was not sent from the claimed domain or the message has been tampered with.

A typo can cause this in the domain name in the DKIM signature or someone trying to spoof an email address from a domain they do not own.

If you receive an email with an invalid DKIM signature, you should not trust the contents of that email.

What should you do if your DKIM signature is invalid?

DKIM verifies the origin and integrity of email messages. When DKIM fails, it results in an "Invalid DKIM signature" error. This can be caused by various issues, such as a misconfigured DKIM key, a compromised email server, or spam filters blocking the message.

If your DKIM signature is invalid, you can do a few things to troubleshoot and fix the issue. First, you have correctly added your DKIM signature to your email messages. If you are not sure how to do this, consult the instructions provided by your email provider or DKIM service.

Once you have verified that your DKIM signature is correctly set up, check the configuration of your domain's DNS settings. Ensure that the public key for your domain is published in the correct location and that the TXT record for your domain has been updated with the correct values. If you are unsure how to complete these tasks, contact your domain registrar or hosting provider for assistance.

One common mistake we find in the DNS entry for the DKIM key is that it's entered in multiple lines.

Conclusion: What are the benefits of using DKIM, and what should you do if your DKIM signature is invalid?

The purpose of DKIM is to protect the domain name from being used in phishing attacks and to ensure that the email has not been tampered with during transport.

There are many benefits to using DKIM. Firstly, it allows the recipient to verify that the message is from the domain name shown in the "From" header, which can help prevent phishing attacks. Secondly, it can help to ensure that the email has not been tampered with during transport, which can help to protect against spam and malware.

If you see an error message that says "Invalid DKIM signature", either your domain name is not configured for DKIM, or there is a problem with your DKIM signature.

In conclusion, an "Invalid DKIM signature" means that the email's authentication has failed. This could be because the message was not sent from the authorized email address or the email server did not correctly apply the DKIM signature. If you receive this error message, it's best to contact the sender to verify the email's legitimacy.