What is Domain Keys Identified Mail?
What is DomainKeys Identified Mail (DKIM)? A Complete Guide to Email Authentication
DomainKeys Identified Mail (DKIM) is an email authentication method that helps verify whether an email message is genuinely from the sender it claims to be from. Unlike traditional email authentication methods, DKIM uses cryptographic techniques to add a digital signature to the email header. This signature can then be verified by the recipient’s mail server to confirm the authenticity of the message and ensure it hasn’t been tampered with during transit.
In simple terms, DKIM ensures that the contents of the email remain intact and authentic, protecting against email spoofing and phishing attacks.
How Does DKIM Work?
DKIM works by using a pair of cryptographic keys: a private key and a public key. These keys are used to create and verify the DKIM signature that is included in the email header. Here’s a step-by-step breakdown of how DKIM works:
- Generating the DKIM Signature
When an email is sent, the sender’s email server uses a private key to create a unique cryptographic signature for the message. This signature is generated based on various parts of the email, such as the subject, body, and headers. The signature is then added to the email header. - Sending the Email
The email is sent to the recipient, including the DKIM signature in the header. The signature acts as a digital fingerprint of the email, ensuring that any changes made to the email content will invalidate the signature. - Verifying the DKIM Signature
When the recipient’s mail server receives the email, it extracts the DKIM signature and uses the sender’s public key (published in the domain’s DNS records) to verify the signature. The public key allows the recipient’s server to decrypt the signature and compare it to the content of the email. If the content hasn’t been altered, the verification is successful. - Action Based on Verification
If the DKIM verification is successful, the email is considered authentic, and the recipient’s mail server can safely deliver it to the inbox. If the verification fails, the email may be flagged as suspicious, marked as spam, or rejected altogether, depending on the email security policy set by the recipient.
Why is DKIM Important?
- Email Security
DKIM enhances email security by ensuring that emails cannot be altered in transit and that they genuinely come from the sender they claim to represent. This helps protect both individuals and organisations from email spoofing, a common tactic used in phishing attacks. - Preventing Phishing and Spoofing
Phishing attacks often rely on attackers impersonating legitimate organisations to trick recipients into revealing sensitive information. DKIM prevents attackers from spoofing your email address, ensuring that recipients can trust emails that appear to come from your domain. - Email Integrity
DKIM ensures that the contents of the email remain intact and have not been tampered with during transmission. This guarantees the integrity of the message and ensures that recipients receive the email exactly as it was sent, without any modifications. - Improving Deliverability
Email providers like Gmail, Yahoo, and Microsoft use DKIM as part of their anti-spam and anti-phishing measures. Emails that are DKIM-authenticated are more likely to pass through spam filters and reach the recipient’s inbox, improving overall deliverability. - Building Trust
Implementing DKIM helps build trust with your recipients. When email clients see that your domain is protected with DKIM, they can be more confident that emails from your domain are legitimate, improving your brand’s reputation.
DKIM vs. Other Email Authentication Methods
While DKIM is an important part of email authentication, it works best when used in conjunction with other protocols such as SPF (Sender Policy Framework) and DMARC (Domain-based Message Authentication, Reporting & Conformance).
- SPF: SPF allows the recipient’s mail server to verify if an email is coming from an authorised mail server. It checks the sender’s IP address against a list of allowed senders in the domain’s DNS records.
- DMARC: DMARC builds on DKIM and SPF by adding a reporting mechanism and specifying how emails that fail authentication should be treated (i.e., whether they should be quarantined or rejected).
Together, these three protocols form a comprehensive email security system, making it much harder for attackers to send fraudulent emails from your domain.
How to Implement DKIM
- Set Up DKIM in Your Email Server
The first step is to configure DKIM on your email server. This typically involves generating a public/private key pair and configuring your email software to sign outgoing emails with the private key. - Publish the Public Key in DNS
The public key must be published in your domain’s DNS records. This allows recipient email servers to retrieve the public key and verify the DKIM signature in the email header. - Test DKIM Configuration
After setting up DKIM, use online tools to test whether your DKIM configuration is working correctly. This will help identify any issues before you start sending emails to recipients. - Monitor DKIM Reports
If you are also using DMARC, you can receive reports on the success or failure of DKIM authentication. This allows you to monitor how your DKIM implementation is performing and make adjustments if necessary.
Conclusion
DomainKeys Identified Mail (DKIM) is an essential tool for protecting your email communication from spoofing and tampering. By using cryptographic techniques to authenticate emails, DKIM ensures that the sender’s identity is legitimate and that the message’s integrity is maintained.
Talk to us about our Shield package for your cybersecurity needs. For more information about how we can help you with your business IT needs, call us on 0333 444 3455 or email us at sales@cnltd.co.uk.
