DKIM (DomainKeys Identified Mail) is an email security standard that organizations need to make the most of to identify and detect email security threats if the email conversation appears altered in transit. This text provides a brief overview of the DKIM protocol, its need, and the best practices to follow when implementing the DKIM protocol.
What is DKIM?
DKIM is a technique used for authenticating emails to allow recipients to verify the legitimacy of an email source. The DKIM ensures the email sender is genuine by attaching a digital signature in the email’s header. Furthermore, the DKIM employs encryption techniques and improves email deliverability and security.
Why do you need DKIM?
There are nearly 4.258 billion email users in 2022, a number expected to rise to 4.594 billion in the next three years. With emails serving as the primary source of conveying and exchanging information worldwide, there is a huge need to ensure the authenticity of an email, especially in the corporate world, a service fulfilled by the DKIM protocol.
An adequately configured DKIM protocol used in conjunction with SPF (Sender Policy Framework) and DMARC (Domain-based Message Authentication Reporting and Conformance) for outbound SMTP can ensure a robust email security and domain security posture.
DKIM Best Practices You Need to Implement
Here are some of the best practices that you need to know to employ while using DKIM protocol:
- Key Length: The key length is an important attribute to pay attention to while configuring the DKIM. A 1024-bit or 2048-bit key length has increased complexity, making it significantly harder for threat actors to break it. 512 or lower bit keys are easily unscrambled due to the decreased key size.
- Key Rotation: Key rotation refers to updating the encryption key. It would be best to rotate DKIM keys at least twice a year to limit the time a key is exposed and used. You can also rotate it quarterly for better protection.
- Signature Expiration: The expiration period for email signatures should be greater than the key rotation time as they can result in getting a DKIM failure on all inboxes. In addition, utilizing signature expiration can assist with new DKIM key management by reducing the risk of cybercriminals accessing older keys to trick or harm email recipients using malicious emails.
- Monitoring: A DMARC policy is built on SPF and DKIM mechanisms to standardize email authentication. DMARC policies also provide a monitoring mode by defining the policy as none. You can set “p=none” to instruct DMARC to give reports on the outbound SMTP’s origin without affecting its deliverability. Furthermore, you can also use the DNS (Domain Name System) to monitor the frequency of key queries.
- Hashing Standards: DKIM uses hashing of headers and content to sign emails digitally. Implementing the SHA256 (Secure Hash Algorithm 256-bit) offers better security over SHA1 as the latter is easily broken due to its smaller size.
- Third-Party Mailers: Standardizing proper DKIM implementations and email security standards for third-party vendors that can exchange emails on your organization’s behalf can go a long way to secure emails and increase customer trust.
- Testing: Organizations and individuals can also check if their DKIM protocol is working correctly via the testing mode. You can indicate the DKIM test mode by specifying “t=y.” However, it would be best to change the value to “t=s” before DKIM deployment; otherwise, the mail provider would disregard the DKIM signature.
Essential Checks to Perform Before and After Implementing DKIM
Organizations should perform a quick check for their organization’s DKIM policy or before deployment, keeping in mind the following points:
- All sending systems support the DKIM.
- Ensuring the existence of a public key corresponding to each private one.
- DKIM employs a 1024 or higher bit encryption key.
- All emails are DKIM signed.
- Revoke any compromised keys.
- Ensure the DKIM key is free of syntax errors.
- Configure DMARC records to ensure DKIM and SPF authentication.
- Employ regular key rotation.
In the age where email security and authenticity are of utmost importance, employing a strong DKIM by following the best practices for DKIM provided in this article can help strengthen your outbound SMTP. Performing regular checks on the DKIM and DMARC policies can help maintain top-of-the-line security to establish a trustworthy, secure, and robust email deliverability and spam filtering process to protect against email-borne cyber threats.