Summary
The distinction between DomainKey and DKIM, or DomainKeys Identified Mail, is a common point of confusion for those new to email authentication. In essence, DomainKeys was an earlier email authentication standard that aimed to verify the sender of an email and ensure its integrity during transit. DKIM is its successor, an evolved and more robust protocol that builds upon the foundational concepts of DomainKeys. DKIM offers greater flexibility and security features, making DomainKeys largely obsolete and unsupported in modern email environments. Implementing DomainKey-Signature today is generally advised against due to its deprecation and lack of widespread support.
Key findings
- Successor standard: DKIM is the modern and widely adopted email authentication standard, effectively replacing its predecessor, DomainKeys.
- Shared goal: Both protocols use public/private key cryptography and DNS records to authenticate sending domains and verify message integrity.
- Enhanced capabilities: DKIM introduces improvements such as clearer signatory identification and more granular signing options, which were not present in DomainKeys.
- Deprecation: DomainKeys has been officially deprecated and is no longer actively maintained or supported by most email service providers or receiving mail servers.
Key considerations
- Modern relevance: Focus efforts on implementing and maintaining DKIM, SPF, and DMARC for optimal email deliverability, as these are the current industry standards.
- Provider support: Most email providers and MTAs do not support DomainKey-Signature generation or validation anymore. Confirm with your provider if you encounter older systems.
- Resource allocation: Attempting to implement DomainKeys can be a futile exercise, consuming valuable resources for a system that provides no real-world benefit.
- Deliverability impact: Mailbox providers rely on DKIM and other current authentication protocols to filter spam and phishing, meaning DomainKeys offers no deliverability advantage. Ensure your DKIM configuration is correct.
What email marketers say
Email marketers and technical professionals frequently encounter questions about legacy authentication methods like DomainKeys, especially when dealing with older systems or reviewing historical email configurations. The overwhelming consensus within the community is that DomainKeys is an outdated technology, superseded by DKIM, and offers no practical benefit for modern email deliverability.
Key opinions
- Historical context: DomainKeys served as a precursor to DKIM, laying the groundwork for digital signature-based email authentication.
- Redundant effort: Attempting to implement DomainKeys today is seen as a waste of time and resources, as it is no longer checked by most receiving mail servers.
- Outdated systems: If a system is still signing emails with DomainKeys, it likely indicates a need for significant modernization and maintenance.
- Performance impact: Signing emails with an additional, deprecated key can consume unnecessary CPU resources and potentially slow down email delivery throughput.
Key considerations
- Focus on DKIM: Prioritize the correct implementation and monitoring of DKIM for your email streams.
- Resource optimization: Avoid allocating development or operational resources to support DomainKeys, as it yields no deliverability or security advantage.
- Software compatibility: Modern MTA software and email platforms are unlikely to offer native support for DomainKeys signing, requiring custom or legacy integrations that are risky and unstable.
- Security implications: Relying on outdated email authentication can potentially create blind spots in your overall email security posture. For effective authentication, understanding how DKIM works is key.
Marketer view
Marketer from Email Geeks states that DomainKeys, as a standard, has been largely deprecated by the more advanced DKIM protocol, indicating a clear progression in email authentication technologies.
Marketer view
A deliverability expert from SocketLabs observes that while DomainKeys was an early domain-level authentication standard, it has been effectively superseded by DKIM, which offers enhanced flexibility and robustness for current email needs.
What the experts say
Experts in email deliverability and security uniformly agree that DomainKeys is an antiquated system that has been entirely superseded by DKIM. They emphasize that any effort spent on implementing or maintaining DomainKeys is misguided, as modern mail systems do not rely on it for authentication. The focus for robust email security and deliverability must remain squarely on current standards like DKIM, SPF, and DMARC.
Key opinions
- No contemporary relevance: DomainKeys has no practical impact on email deliverability or spam filtering in today's email ecosystem.
- Industry consensus: The email industry has moved on, and all major mailbox providers and security vendors prioritize DKIM.
- Maintenance burden: Systems still attempting to use DomainKeys are operating with legacy configurations that are difficult to maintain and likely pose more risks than benefits.
- Security best practice: Adopting and correctly configuring modern email authentication protocols is critical for protecting against phishing, spoofing, and ensuring trusted communication.
Key considerations
- Upgrade systems: If your sending infrastructure still references or attempts to use DomainKeys, it's imperative to update to fully support DKIM.
- Resource reallocation: Direct engineering and IT resources towards optimizing DKIM signing, managing DKIM keys, and analyzing DMARC reports.
- Avoid unnecessary complexity: Do not introduce a deprecated standard into your email flow, as it only adds complexity without benefit.
- Forward compatibility: Ensure your authentication strategy aligns with future standards and current best practices, not historical ones. Learn more about the differences between DomainKeys and DKIM.
Expert view
Deliverability expert from SpamResource observes that the email industry has thoroughly transitioned to DKIM, making DomainKeys practically irrelevant for contemporary email authentication procedures.
Expert view
An authority from WordtotheWise points out that relying on deprecated standards like DomainKeys can lead to significant deliverability problems, as receiving mail servers no longer validate them or treat them as a factor in reputation.
What the documentation says
Technical documentation, particularly Request for Comments (RFCs) from the Internet Engineering Task Force (IETF), clarifies the historical progression from DomainKeys to DKIM. RFCs detail the specifications, evolution, and eventual deprecation of DomainKeys in favor of the more comprehensive and robust DKIM standard. They outline the cryptographic mechanisms and DNS interactions that underpin both, emphasizing DKIM's enhancements for wider applicability and security.
Key findings
- RFC 4870: This RFC details the original, experimental mechanism for DomainKeys, focusing on verifying the sending domain and message integrity.
- RFC 6376: This is the definitive specification for DKIM, which supersedes and expands upon DomainKeys, providing the current standard for email signing.
- Architectural improvements: DKIM improves upon DomainKeys by allowing for distinct roles between the message author and the signing entity, among other enhancements.
- Standardization: The IETF's adoption of DKIM as a full standard, rather than experimental, solidified its position as the preferred authentication method.
Key considerations
- Refer to current RFCs: Always consult the latest RFCs for email authentication (e.g., RFC 6376 for DKIM) when implementing or troubleshooting.
- Backward compatibility: While DKIM is broadly compatible, attempting to explicitly implement DomainKeys is not required for interoperability and may cause issues.
- Understanding evolution: Grasping the evolution from DomainKeys to DKIM helps in understanding the design principles and robust features of current authentication standards.
- Impact on parsing: Modern email parsers and security gateways are optimized to process DKIM signatures, not DomainKeys, reinforcing the need to move beyond the older protocol. Reviewing the basics of DKIM signatures is advisable.
Technical article
The IETF (RFC 6376) documentation clearly defines DKIM as a mechanism for an entity to assert responsibility for transmitting a message, enabling recipients to validate that assertion through cryptographic means.
Technical article
An RFC (RFC 4870) from the Internet Engineering Task Force describes DomainKeys as an experimental protocol used to verify the domain of an email sender and confirm the integrity of the message content.
Related resources
12 resources
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