Summary
Across various sources, including email experts, marketers, and official documentation, there's a consistent consensus that the order of mailto: and https: in the List-Unsubscribe header doesn't strictly matter from a specification standpoint. RFCs mandate the presence of an HTTPS URL, but not its position relative to other methods. While most user agents are free to choose which method to use, one expert suggests prioritizing HTTPS to avoid issues with poorly written unsubscribe parsers.
Key findings
- No Order Specification: The email standards (RFCs) do not specify a particular order for mailto: and https: within the List-Unsubscribe header.
- HTTPS Requirement: An HTTPS URL is required in the List-Unsubscribe header per RFC 8058.
- MUA Discretion: Mail User Agents (MUAs) have the flexibility to choose which unsubscribe method to utilize.
Key considerations
- Parser Compatibility: While not a standard requirement, placing HTTPS first may improve compatibility with older or poorly written unsubscribe parsers.
- Best Practice: Including both mailto: and HTTPS offers broader compatibility and redundancy for users.
- Testing: Thoroughly test your List-Unsubscribe implementation to ensure both methods function correctly across diverse email clients.
What email marketers say
8 marketer opinions
Multiple email marketing resources agree that including a List-Unsubscribe header is a best practice for email deliverability. While it's common to provide both mailto: and HTTPS options within the header, most sources do not specify or enforce a particular order for these options. User agents are generally free to choose which method to use when multiple options are available.
Key opinions
- No Enforced Order: Most platforms do not enforce a specific order of mailto: and HTTPS in the List-Unsubscribe header.
- User Agent Choice: User agents (email clients) can choose which unsubscribe method to use when multiple options are presented.
- Importance of Header: Implementing a List-Unsubscribe header, regardless of order, improves deliverability.
Key considerations
- HTTPS is Preferred: Though order isn't strictly enforced, some sources suggest that HTTPS should come first for compatibility reasons as a modern best practice.
- Testing: Always test your List-Unsubscribe implementation to ensure both mailto: and HTTPS options function correctly across different email clients.
- Multiple Entries: Avoid using multiple entries of the same type (e.g., multiple HTTPS URLs) as it may lead to unexpected behavior and is generally not recommended.
Marketer view
Email marketer from Gmass explains the importance of the List-Unsubscribe header for deliverability but doesn't touch on mailto vs https order.
14 May 2024 - Gmass
Marketer view
Email marketer from Litmus highlights the value of List-Unsubscribe, but the article does not reference an order of preference of the options.
30 Apr 2025 - Litmus
What the experts say
3 expert opinions
Experts generally agree that the order of mailto: and https: in the List-Unsub header doesn't have a specified meaning according to email standards (RFC8058). The MUA (Mail User Agent) ultimately decides which method to use. However, one expert advises against placing the mailto: option first, citing potential issues with poorly written unsubscribe parsers.
Key opinions
- No Specified Order: Email standards don't mandate a specific order for mailto: and https: in the List-Unsub header.
- MUA Preference: The Mail User Agent (MUA) determines which unsubscribe method to use.
- HTTPS required: RFC8058 requires an https option within the List-Unsub header
Key considerations
- Parser Issues: Some poorly written unsubscribe parsers might incorrectly handle the mailto: option if placed first.
- Prioritization: Even though order isn't strictly defined, it may be prudent to prioritize the HTTPS option.
Expert view
Expert from Email Geeks explains that there is no specification meaning to the order of List-Unsub header. As far as RFC8058 is concerned, you have to have an https one and that’s it. And everyone who supports it will use that out of preference over the mailto:, regardless of order.
27 Feb 2024 - Email Geeks
Expert view
Email marketer from Email Geeks shares that no order is required for the List-Unsub header. The preference of what to use is up to the MUA.
6 May 2023 - Email Geeks
What the documentation says
3 technical articles
Email deliverability documentation emphasizes that while the List-Unsubscribe header is crucial for a one-click unsubscribe mechanism, the order of different unsubscribe methods (mailto:, https:) is not specified. Including both methods is suggested, with the HTTPS version mandated by RFC 8058, but no particular order is prescribed within the header.
Key findings
- No Order Specified: Email standards (RFCs) do not specify a particular order for unsubscribe methods in the List-Unsubscribe header.
- HTTPS Mandate: The presence of an HTTPS URL in the List-Unsubscribe header is mandated by RFC 8058.
- Both Methods Recommended: Including both mailto: and HTTPS versions is a suggested best practice, although order is not dictated.
Key considerations
- Compliance: Ensure your List-Unsubscribe header includes an HTTPS URL to comply with RFC 8058.
- Testing: Test your List-Unsubscribe implementation to verify both unsubscribe methods function correctly.
Technical article
Documentation from ietf.org specifies that the List-Unsubscribe header field is intended to provide a simple, one-click unsubscribe mechanism for mailing lists. It does not specify any particular order for the multiple unsubscribe methods (e.g., mailto:, http:).
18 Oct 2022 - ietf.org
Technical article
Documentation from SparkPost details the List-Unsubscribe header, including implementation. They do not specify order, but suggest including both mailto and https versions.
27 Jun 2023 - SparkPost
Are mailto links compliant with Google and Yahoo's one-click unsubscribe requirements?
Do subscription based emails require a list unsubscribe option according to Gmail and Yahoo's new sending requirements?
Does Google require List-Unsubscribe for one-click unsubscribe in emails?
How are Gmail and Yahoo enforcing unsubscribe requests, and what factors do they consider for compliance?
How can I verify if my company's emails have List-Unsubscribe headers correctly configured?
How do Gmail and Yahoo's new one-click unsubscribe requirements work?
How do I add an unsubscribe button to the email header and what is RFC 8058?
Is 'reply to unsubscribe' an acceptable unsubscribe option post Yahoo and Google's new requirements?
What are the Gmail sender requirements for one-click unsubscribe, and where should the links be placed?
