DKIM (DomainKeys Identified Mail) and DMARC (Domain-based Message Authentication, Reporting & Conformance) are both email authentication methods that are used to help protect email recipients from receiving email messages that are not legitimate.
DKIM
- DKIM uses a digital signature, which is included in the header of an email message, to confirm that the message was sent by an authorized sender.
- The digital signature is generated using a private key, which is held by the sender, and can be verified by the recipient using the corresponding public key, which is published in the sender's DNS records.
- The digital signature is used to confirm that the message has not been modified in transit and that it was sent by the domain that it claims to be sent from.
DMARC
- DMARC is built on top of SPF (Sender Policy Framework) and DKIM, and it allows a domain owner to publish a policy in their DNS records that specifies which mechanisms are used for email authentication for their domain and how the receiving mail server should handle messages that fail authentication.
- DMARC also provides a mechanism for email receivers to report back to the domain owner about messages that pass or fail DMARC evaluation.
- DMARC allows a domain owner to specify a "policy" for their domain which can be one of "none", "quarantine" or "reject". "none" means that the receiving mail server should take no action, "quarantine" means that the receiving mail server should treat the message as suspicious, and "reject" means that the receiving mail server should reject the message outright.
Comparison Table DMARC with DKIM
| Feature | DKIM | DMARC |
|---|---|---|
| Purpose | Verify the authenticity of the message | Verify the authenticity of the message and control how it's handled by the recipient |
| Mechanism | Digital signature | Combines SPF and DKIM and adds policy control |
| Key management | Uses private key | Uses DKIM and SPF keys |
| Reporting | No | Yes, sends feedback to domain owner |
Both DKIM and DMARC are used to authenticate email messages and protect recipients from receiving email messages that are not legitimate. However, DMARC builds upon DKIM and provides additional functionality, such as the ability for a domain owner to publish a policy for their domain and to receive feedback about messages that pass or fail DMARC evaluation.
Common Question and Answers DMARC and DKIM
What is the purpose of DKIM and DMARC?
DKIM (DomainKeys Identified Mail) is an email authentication method that is used to verify the authenticity of an email message by using a digital signature. The digital signature is included in the header of an email message and can be verified by the recipient using the corresponding public key, which is published in the sender's DNS records.
DMARC (Domain-based Message Authentication, Reporting & Conformance) builds on top of DKIM and is used to verify the authenticity of an email message, as well as control how the message is handled by the recipient. A domain owner can publish a policy in their DNS records that specifies which mechanisms are used for email authentication for their domain and how the receiving mail server should handle messages that fail authentication. DMARC also provides a mechanism for email receivers to report back to the domain owner about messages that pass or fail DMARC evaluation.
How do DKIM and DMARC differ from SPF?
SPF (Sender Policy Framework) is another email authentication method that is used to confirm that an email message was sent by an authorized sender. However, while SPF only verifies the identity of the sender, DKIM and DMARC also provide mechanisms to confirm that the message has not been modified in transit and to control how the message is handled by the recipient.
How do I implement DKIM and DMARC for my domain?
Implementing DKIM and DMARC requires publishing specific DNS records for your domain. This includes creating a DKIM TXT record that holds the public key used to verify the digital signature and a DMARC TXT record that holds the policy for your domain. There are various tutorials and guides available online that can help you with the setup process.
What are the best practices for maintaining DKIM and DMARC?
- Regularly rotate the keys used for DKIM to keep the private key secure.
- Monitor the DMARC reports to ensure that your email is being delivered correctly.
- Stay informed about any updates or changes to the DKIM and DMARC standards.
- Test your DKIM and DMARC implementation using online tools to ensure that it's properly configured.
How does DMARC help prevent phishing?
By implementing DMARC, a domain owner can publish a policy for their domain that specifies which mechanisms are used for email authentication and how the receiving mail server should handle messages that fail authentication. This helps to prevent unauthorized parties from sending messages that appear to be from the domain, and thus reduce phishing attempts.
Is it possible to implement DMARC without DKIM?
No, DMARC builds upon DKIM and SPF (Sender Policy Framework) to authenticate email messages. It is not possible to implement DMARC without first implementing DKIM and SPF.