Summary
When configuring the List-Unsubscribe header in emails, a common question arises regarding the order of MAILTO and HTTPS values. While technical specifications might suggest a particular precedence, real-world implementation by mailbox providers (MBPs) often differs, prioritizing their preferred one-click unsubscribe methods.
Key findings
- Technical precedence: From a purely technical standpoint, the order of values in the List-Unsubscribe header typically dictates preference from left to right, meaning the first value listed holds the highest technical priority.
- Mailbox provider preference: Despite technical precedence, mailbox providers often reorder or select the method they prefer, such as an HTTPS one-click unsubscribe URL, regardless of its position.
- Historical issues: In the past, some providers (notably Microsoft) had specific behaviors where the order might have mattered. These instances are largely resolved today.
- Google's specific guidance: Historically, Google recommended placing the HTTPS URL first for proper one-click unsubscribe functionality, suggesting that order could impact feature adoption. Modern requirements (RFC 8058) dictate the presence of an HTTPS URL for one-click, but not a strict order relative to MAILTO.
Key considerations
- Prioritize one-click: Given the widespread adoption and preference for one-click unsubscribe by major mailbox providers like Gmail and Yahoo, it is best practice to include an HTTPS URL following RFC 8058.
- RFC 8058 compliance: Ensure your List-Unsubscribe header includes at least one HTTPS URI for one-click functionality, regardless of other values. You can read more about RFC 8058 and one-click unsubscribe to learn more.
- Redundancy: Including both MAILTO and HTTPS links provides fallback options for various email clients and ensures accessibility for all users.
- Monitoring: Regularly monitor List-Unsubscribe compliance and unsubscribe rates to identify any deliverability issues. Review our guide on how List-Unsubscribe links impact sender reputation.
What email marketers say
Email marketers often approach the List-Unsubscribe header from a practical perspective, focusing on what works in real-world scenarios rather than strict technical adherence. Their experiences highlight the nuances of how different mailbox providers interpret and prioritize the unsubscribe options, particularly concerning one-click functionality.
Key opinions
- Practical functionality: Many marketers find that the order often doesn't visibly impact the unsubscribe experience for most users, as email clients tend to display the most preferred method (typically HTTPS one-click).
- Preference override: Mailbox providers are seen as dictating the preference, regardless of how the MAILTO and HTTPS options are ordered in the header itself.
- Impact on one-click: Some anecdotal evidence suggests that placing MAILTO first might have previously reduced the likelihood of RFC 8058 one-click unsubscribes being registered by certain providers, particularly Google.
Key considerations
- Default to HTTPS first: To maximize the chance of one-click functionality being recognized, many marketers prefer to put the HTTPS URL first in the List-Unsubscribe header.
- Testing is key: Regularly test how your List-Unsubscribe headers perform across different email clients and mailbox providers. You can use an email deliverability tester to check your setup.
- Compliance requirements: Marketers must ensure their unsubscribe headers comply with the latest requirements from major players like Yahoo and Gmail, which heavily emphasize the HTTPS one-click option.
Marketer view
Email marketer from Email Geeks states that they've placed MAILTO first and HTTPS second in the List-Unsubscribe header, and it continues to function as expected without issues.
Marketer view
Email marketer from Email Geeks mentions that they don't believe the order fundamentally matters because email providers will ultimately prioritize their preferred unsubscribe method.
What the experts say
Email deliverability experts typically emphasize adherence to technical specifications and the practical implications of mailbox provider behavior. While the RFCs provide a baseline, the real-world application often involves adaptations to ensure optimal performance and compliance with evolving industry standards, particularly around one-click unsubscribe functionality.
Key opinions
- Strict technical order: Technically, the List-Unsubscribe header's values are processed from first to last, implying a preference based on their order in the string.
- Mailbox provider overrides: In practice, mailbox providers have their own preferences, and they will select the protocol they favor for an unsubscribe action, often overriding the sender's specified order.
- Historical nuances: While there were historical instances where ordering (e.g., with Microsoft) might have impacted behavior, these are generally not relevant today.
Key considerations
- Prioritize current standards: Focus on complying with the latest industry standards and RFCs, particularly RFC 8058 for one-click unsubscribe, which mandates an HTTPS URL.
- Embrace one-click: Given its benefits for deliverability and user experience, ensure that HTTPS one-click unsubscribe is correctly implemented and readily available. This helps with email deliverability issues.
- Sender reputation: A properly configured List-Unsubscribe header, especially with one-click, contributes positively to sender reputation by reducing spam complaints.
Expert view
Deliverability expert from Email Geeks indicates that, from a technical perspective, the preference for List-Unsubscribe values is generally from first to last in the header string.
Expert view
Deliverability expert from Email Geeks clarifies that while technical order exists, in practice, mailbox providers will often prioritize the unsubscribe protocol they prefer, regardless of its position in the header.
What the documentation says
Official documentation, primarily RFCs, provides the foundational guidelines for the List-Unsubscribe header. While older RFCs offered flexibility, newer specifications like RFC 8058 have introduced stricter requirements, especially for one-click functionality, which directly influences the expected behavior of email clients and providers.
Key findings
- RFC 2369 precedence: According to RFC 2369, which defines the List-Unsubscribe header, multiple URLs (including mailto and http/https) can be included, and client implementations might choose the first one or a preferred one.
- RFC 8058 mandate: For one-click unsubscribe to be valid, RFC 8058 states that the List-Unsubscribe header must include a HTTPS URI, even if a mailto URI is also present.
- Order not explicitly mandated by RFC 8058: While RFC 8058 makes the HTTPS URI a requirement for one-click, it does not explicitly state that the HTTPS link must precede a MAILTO link.
Key considerations
- Adherence to RFC 8058: For maximum compatibility and to leverage one-click unsubscribe, ensuring the presence of a properly configured HTTPS URL as per RFC 8058 is paramount, regardless of other links. You can read the full RFC 8058 documentation here.
- Backward compatibility: Including a mailto URI (as specified in older RFCs like RFC 2369) alongside the HTTPS one provides a fallback for clients that may not fully support newer standards.
- Evolution of standards: Be aware that email standards evolve, and what was optional or flexible in older RFCs (like RFC 5322) may become mandatory or have specific implications in newer ones.
Technical article
Documentation from Mailgun states that to be valid for one-click unsubscribe under RFC 8058, the List-Unsubscribe header must contain an HTTPS URI, although mailto links can also be present.
Technical article
Documentation from RFC 2369, the original standard for List-Unsubscribe, specifies that the header can contain one or more URLs, including both mailto and http/https schemes, leaving the choice to the email client.
Related resources
9 resources
Related pages
How does the List-Unsubscribe header affect email deliverability with a preference center?
How do List-Unsubscribe headers function with one-click, mailto, and HTTP links, and what are their implications for sender reputation?
What are the requirements for List-Unsubscribe headers to comply with Yahoo and Gmail?
Is implementing a list-unsubscribe header mandatory for Gmail and Yahoo and what are the impacts?
Does Google require List-Unsubscribe for one-click unsubscribe in emails?
Is the one-click unsubscribe / list-unsubscribe header a requirement for marketing emails?
Are mailto links compliant with Google and Yahoo's one-click unsubscribe requirements?
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