Summary
While not strictly mandated by RFC specifications or DKIM standards, aligning the DKIM domain with the List-Unsubscribe domain is generally considered a 'best practice' that enhances email deliverability and sender reputation. Although alignment isn't a hard requirement, various sources suggest that it strengthens sender authentication, builds trust with mailbox providers, improves deliverability rates, reduces the risk of being flagged as spam, and positively influences placement rates. It is crucial that the List-Unsubscribe headers are DKIM signed. Furthermore, having a clear and working unsubscribe process is a core element for compliance and deliverability.
Key findings
- Not Mandated by RFC/DKIM: RFC specifications and DKIM standards do not explicitly require DKIM domain alignment with the List-Unsubscribe domain.
- DKIM Signing of Headers: List-Unsubscribe headers must be signed with DKIM.
- Best Practice for Deliverability: Aligning DKIM and List-Unsubscribe domains is a 'best practice' that generally improves deliverability and sender reputation.
- Strengthens Authentication: Domain alignment strengthens sender authentication and builds trust with mailbox providers.
- Improves Placement Rates: Alignment can positively influence email placement rates and reduce the risk of spam flagging.
- Core Unsubscribe Process: Clear and working unsubscribe process is vital for compliance and deliverability.
- Part of a Larger Strategy: Email authentication is a complex issue, domain keys are one component of this. Domain alignment plays a supporting role.
Key considerations
- Mailbox Provider Policies: Be aware of stricter policies from mailbox providers (e.g., Gmail, Yahoo) that may benefit from alignment.
- Authentication Methods: Implement comprehensive email authentication methods, including DKIM, SPF, and DMARC.
- Testing and Validation: Use testing tools to verify email authentication and improve deliverability.
- Content Stability: Ensure content remains unchanged after DKIM signing to maintain signature validity.
- Domain Reputation: Maintain a good domain reputation for optimal email deliverability.
- Clear Unsubscribe Process: Prioritize a clear, easy, and functional unsubscribe process.
What email marketers say
10 marketer opinions
While not strictly mandatory according to RFC standards, aligning the DKIM domain with the List-Unsubscribe domain is widely considered a 'best practice' for enhancing email deliverability and sender reputation. Although not a hard requirement, domain alignment strengthens sender authentication, building trust with mailbox providers like Gmail and Yahoo. Most sources recommend aligning the domains, as it helps legitimize email, reduce the risk of being flagged as spam, and positively influence placement rates, especially when combined with other authentication methods like SPF and DMARC. Testing tools can also help verify authentication and improve deliverability.
Key opinions
- Not Mandatory: RFC standards do not mandate alignment between DKIM and List-Unsubscribe domains.
- Best Practice: Alignment is generally considered a 'best practice' for improved deliverability.
- Builds Trust: Consistent domains build trust with mailbox providers.
- Strengthens Authentication: Domain alignment strengthens sender authentication.
- Influences Placement: Positively influences placement rates and reduces spam flagging.
- Testing Is Key: Testing tools can help verify authentication and improve deliverability scores.
Key considerations
- Sender Reputation: Consider aligning domains to improve sender reputation and trustworthiness.
- Mailbox Provider Requirements: Be aware of stricter requirements from mailbox providers like Gmail and Yahoo.
- Email Authentication: Prioritize proper domain authentication, including DKIM, SPF, and DMARC.
- Combine Methods: Combine domain alignment with other authentication methods for optimal results.
- Working Unsubscribe: Ensure a clear and functional unsubscribe process, as its an important part of deliverability.
Marketer view
Email marketer from Mailjet explains that while alignment isn't strictly enforced, it's a good practice for deliverability. Having consistent domains builds trust with mailbox providers.
31 Aug 2022 - Mailjet
Marketer view
Marketer from Email Geeks shares that the DKIM and the List-unsubscribe do not have to align. The main requirements are A valid DKIM Signature and `List-Unsubscribe` and `List-Unsubscribe-Post` in the `h=`
23 Oct 2022 - Email Geeks
What the experts say
4 expert opinions
While DKIM signing of List-Unsubscribe headers is crucial, strict domain alignment isn't necessarily mandated. Expert opinions suggest that having a working unsubscribe process is more vital for compliance and deliverability. Email authentication, including DKIM, is a complex part of a broader deliverability strategy, where domain alignment plays a supporting but not central role. Changing content after DKIM signing will invalidate the signature.
Key opinions
- DKIM Signing Required: List-Unsubscribe headers must be signed with DKIM.
- No Mandatory Alignment: Domains of DKIM and List-Unsubscribe do not strictly need to align.
- Unsubscribe Process Priority: A functional unsubscribe process is vital for compliance and deliverability.
- DKIM Part of Larger Strategy: Domain alignment is part of a larger email authentication strategy.
- Content Changes Invalidate Signature: Changing content post-DKIM signing invalidates the signature.
Key considerations
- Implement DKIM Signing: Ensure List-Unsubscribe headers are properly signed with DKIM.
- Prioritize Unsubscribe Functionality: Focus on creating a clear and reliable unsubscribe process.
- Consider Authentication Strategy: Develop a comprehensive email authentication strategy.
- Pre-Sign Content Stability: Avoid altering content after DKIM signing to maintain validity.
- Consider Domain Reputation: Although not a requirement, domain reputation still impacts placement rates.
Expert view
Expert from Word to the Wise discusses how email authentication is a complex issue and domain keys are one small component. She states that while domain alignment might help, its a small part of a larger piece.
24 Aug 2023 - Word to the Wise
Expert view
Expert from Email Geeks clarifies that if you change the content between the time the message is signed and when the signature is checked then dkim will fail.
2 Jul 2024 - Email Geeks
What the documentation says
4 technical articles
While the RFC specifications for List-Unsubscribe headers and DKIM standards don't explicitly mandate alignment between the DKIM domain and the List-Unsubscribe domain, DMARC documentation and recommendations from sources like SparkPost suggest that DKIM alignment, in general, enhances deliverability and sender reputation. Consistent domain usage is encouraged to improve email security.
Key findings
- RFC Does Not Require: RFC specifications for List-Unsubscribe do not explicitly require DKIM domain alignment.
- DKIM Standard Doesn't Specify: The DKIM standard does not outline requirements for alignment with List-Unsubscribe or other headers.
- DMARC Recommends Alignment: DMARC documentation recommends DKIM alignment for better email security and deliverability.
- Alignment Improves Deliverability: Overall DKIM alignment (though not specifically List-Unsubscribe) improves deliverability and sender reputation, per SparkPost.
- Consistent Domain Usage: Consistent domain usage is generally encouraged for improving email security.
Key considerations
- Security: Prioritize email security by implementing DMARC and considering DKIM alignment strategies.
- Deliverability: While not strictly required, alignment can improve deliverability, so consider its impact.
- Reputation: Be aware that domain reputation can affect deliverability, making alignment a strategic choice.
- Compliance: Ensure compliance with email standards and best practices for optimal performance.
- Domain Consistency: Strive for consistency in domain usage across email authentication methods to enhance trust.
Technical article
Documentation from DMARC.org focuses on SPF and DKIM alignment for domain-based message authentication, reporting, and conformance (DMARC), and recommends DKIM alignment for better email security and deliverability.
14 Jan 2024 - DMARC.org
Technical article
Documentation from SparkPost highlights that DKIM alignment improves deliverability and sender reputation. Though a direct requirement for List-Unsubscribe domain alignment isn't stated, consistent domain usage is encouraged.
10 Sep 2024 - SparkPost
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