How do I implement DomainKeys and is it still a relevant email authentication method?

Key findings

• Obsolete technology: DomainKeys is an outdated protocol, having been formally obsoleted by DKIM (RFC 4871) in 2007. There is little to no practical benefit in deploying it for current email deliverability.
• Historical relevance: It served as a precursor to DKIM, contributing concepts that are fundamental to how email authentication works today. Understanding its history can be academically interesting.
• Limited receiver checks: Major email service providers, like Gmail and Yahoo, primarily check for DKIM, not DomainKeys, as an authentication factor. While a DomainKeys signature might appear in email headers, it generally does not influence deliverability or authentication results.
• Difficulty in implementation: Finding modern, maintained tools or guides for implementing DomainKeys is challenging due to its obsolescence. It often requires developing custom software or using legacy mail transfer agents (MTAs).

Key considerations

• Focus on DKIM and DMARC: For effective email authentication and deliverability, prioritize the implementation and proper configuration of DKIM, SPF, and DMARC. Learn more about how these standards work.
• Practical skill development: While delving into DomainKeys offers a unique technical challenge, consider focusing on contemporary email authentication methods that provide tangible benefits for deliverability. This can include mastering DKIM authentication and DMARC implementation.
• Avoid unnecessary complexity: Implementing an obsolete protocol adds complexity without improving current email deliverability or security. Resources are better spent on modern best practices.
• Verify current configurations: Ensure your existing SPF, DKIM, and DMARC records are correctly set up and monitored for optimal performance and to adhere to best practices.

Key opinions

• Focus on modern standards: Marketers emphasize the importance of setting up current authentication methods like DKIM, SPF, and DMARC, as these are the ones actively checked by major mailbox providers.
• Deliverability focus: The primary goal is to ensure emails land in the inbox, and obsolete protocols like DomainKeys offer no deliverability advantage.
• Practical skills over historical: While curiosity about older technologies is acknowledged, the advice leans towards investing time in learning and implementing practical skills relevant to current email ecosystems, such as DNS management.
• Limited information: Some acknowledge the general lack of detailed technical information on email marketing and deliverability compared to other areas of software development.

Key considerations

• Avoid outdated practices: Implementing obsolete protocols can be a time sink without any corresponding deliverability benefits. Instead, focus on technical solutions from top performing senders.
• Verify current authentication: Regularly check your current SPF, DKIM, and DMARC configurations to ensure they are correctly set up and aligned, which is crucial for modern email deliverability. Mailchimp also details how to set up email domain authentication.
• Understand auth-results: Learn to interpret email headers, specifically the Authentication-Results header, to see which authentication methods are actually being checked by receiving servers.
• Continuous learning: Given the dynamic nature of email deliverability, continuous learning about current authentication methods and best practices is vital for success.

Key opinions

• Completely obsolete: DomainKeys is no longer relevant for current email authentication, having been superseded by DKIM over 15 years ago.
• Focus on DKIM: DKIM (DomainKeys Identified Mail) is the current standard that evolved from DomainKeys and Cisco's Secure Mail. This is the protocol that should be implemented.
• No practical validation: Since no major receivers check for DomainKeys, validating its correct implementation is difficult and often requires setting up legacy mail systems.
• Better learning opportunities: Time spent on DomainKeys is better invested in learning practical, current skills like DNS management, modern cryptography, and software development, which are more relevant to today's internet infrastructure.
• Yahoo's early implementation: DomainKeys was an early, unvetted implementation by Yahoo that didn't gain traction, eventually leading to the standardized DKIM.

Key considerations

• Prioritize current standards: Focus your efforts on implementing and refining SPF, DKIM, and DMARC. These are the foundations of advanced email authentication.
• Practical skill development: Engage in projects that offer practical, transferable skills in modern email deliverability, such as managing a mail server with contemporary authentication protocols.
• Verify actual checks: Always check Authentication-Results headers to determine which authentication methods are actively being validated by receiving mail servers, rather than relying on the mere presence of a signature.
• Stay updated: Keep abreast of the latest developments in email authentication and deliverability to avoid investing time in deprecated technologies. Check resources like Mailgun's email authentication guide for current best practices.

Key findings

• Formal obsolescence: RFC 4870, which defines DomainKeys, was formally obsoleted by RFC 4871 (DKIM) in 2007, marking its replacement as the industry standard.
• Digital signature core: Both DomainKeys and DKIM rely on digital signatures and public-key cryptography to verify the authenticity of an email's sender and integrity of the message.
• DNS TXT record: The public key for both DomainKeys (historically) and DKIM is published as a DNS TXT record, allowing receiving servers to verify the signature.
• Unified standard: DKIM was created to unify and improve upon prior email signing standards, including DomainKeys, to provide a more robust and widely adopted authentication method.

Key considerations

• Consult RFCs: For a deep dive into the technical specifications, refer directly to RFC 4870 (DomainKeys) and RFC 4871 (DKIM) to understand their mechanisms and relationship. RFC 4870 is available.
• Understand DKIM implementation: Modern documentation focuses heavily on DKIM setup, which typically involves generating key pairs, publishing public keys, and configuring mail servers to sign outbound emails. DuoCircle provides a complete email authentication guide for DKIM.
• Align with current authentication: Ensure your authentication strategy aligns with the requirements of major email providers, which universally prefer and increasingly mandate DKIM and DMARC.
• Review authentication methods: Familiarize yourself with the comprehensive guides available on various email authentication methods, including SPF, DKIM, and DMARC, to ensure full compliance and optimal deliverability.