What is DKIM and Why Is It Important?

An effective way to ensure your emails are not tampered with while on their way to get delivered – is through authentication. Domain-based authentication methods and protocols are significantly effective against email-based cyber attacks, while also helping improve the deliverability of your legitimate emails. DKIM is one such protocol.

It’s based on public key cryptography, and it works by adding a digital signature to the message header. When the receiver gets an email with DKIM, they check the digital signature to make sure it is valid. If it is, then they know the message has remained unaltered during the transfer.

What is DKIM?

DKIM stands for DomainKeys Identified Mail. It is an email authentication protocol that allows senders to prevent email content from being altered during the delivery process. 

It’s based on public key cryptography, and it works by adding a digital signature to the message header. When the receiver gets an email with DKIM, they check the digital signature to make sure it is valid. If it is, then they know the message has remained unaltered during the transfer.

What is a DKIM Header?

A DKIM header is a part of an email that contains the cryptographic DKIM signature. This signature is added by the sender’s mail server. During the authentication process, the signature field in the DKIM header helps verify the authenticity of outbound messages. It helps receivers confirm that the email is genuine and comes from a legitimate sender.

What are DKIM Keys?

DKIM keys are cryptographic private and public key pairs used in DKIM authentication. 

  • Public Key: The DKIM public key is stored in the sender’s DNS and is used by receiving mail servers to verify DKIM signatures.
  • Private Key: The DKIM private key is stored in the sender’s mail server and is appended to each outgoing message as a part of the DKIM header.
How Does DKIM Work?

How Does DKIM Work?

During the DKIM authentication process, the sender’s domain generates a pair of cryptographic keys, and when an email is sent, the sending server adds a DKIM signature to the message header using the private key. 

The sender’s domain publishes the public key in a DNS record. Upon receiving the email, the recipient’s server retrieves the DKIM signature, queries the DNS for the public key, and verifies the signature’s integrity by comparing it to a computed hash of the email’s headers and body. If the signature is valid, the email is considered authentic and unaltered, protecting against forgery and tampering.

How Do I Know DKIM is Working?

To verify that DKIM is indeed working for your domain, you can check your DKIM configuration using our free DKIM checker tool

DKIM Checker Tool

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Enable DKIM with PowerDMARC

PowerDMARC empowers domain owners to set up DKIM along with hands-on monitoring, that helps them stay on top of errors at all times, ensuring deliverability, while actively combatting cyberattacks. 

Our platform is easy to use for businesses of all sizes and can handle multiple domains and large volumes of email traffic. We provide an effective DKIM solution paired with several other essential email authentication protocols for 360-degree protection against email fraud. 

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Frequently Asked Questions on DKIM

To set up DKIM, you need to generate a private key and a corresponding public key, on your mail server with a DKIM record generator. Then, configure your server to sign outgoing emails with the private key and publish the public key as a DNS TXT record for your domain.

To check your DKIM record, you can use our free DKIM checker tool. Simply enter your domain name or the specific DKIM selector you want to check and it will report whether the DKIM record is properly set up or if any issues are detected.

While both are email authentication protocols, SPF focuses on authorizing the domain’s IP address, while DKIM focuses on verifying the email’s integrity and origin.

No, you cannot use the same DKIM key for multiple domains. Each domain requires its own unique DKIM key pair. This ensures that the DKIM signatures are domain-specific and maintains the security and integrity of email authentication for each individual domain.

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Yes, Office 365 supports DKIM. You can configure DKIM signing for your Office 365 domain by generating the necessary DKIM keys and publishing the public key as a DNS TXT record for your domain.

While DKIM is not a mandatory requirement for DMARC (Domain-based Message Authentication, Reporting, and Conformance) implementation, it is highly recommended.

While DKIM provides email authentication on its own, a DMARC analyzer adds an additional layer of control and reporting. While DKIM is not a prerequisite for DMARC, combining DKIM with DMARC yields better email security and visibility into email authentication practices.

There can be several issues surrounding your DKIM implementation. From errors with record configuration and syntax to expired DKIM keys, and improper alignment between headers – each of these problems may result in authentication failures and deliverability issues.

Simply setting up DKIM records for your domains can take anywhere between a few minutes to a few hours or as long as your DNS requires to propagate changes for the newly created record. Post setup, periodic monitoring is the recommended practice as long as you have implemented the protocol.

On an occasion when DKIM fails for your email, it may get flagged as spam or suspicious on the receiver’s side. Depending on your DMARC policy, the mail may even get rejected. Implementing SPF as a fall-back mechanism can be a good option when you are using DKIM with DMARC.

SPF and DKIM are mutually exclusive protocols that can be used separately on their own to authenticate your emails. Implementing SPF, DKIM, and DMARC together makes a power-packed trio that boosts your defenses against spoofing and email phishing attacks.