Suped

Why is Gmail showing '<undefined>' in the List-Unsubscribe header?

8 Marketer opinions3 Expert opinions6 Technical articles2 Resources

Summary

The appearance of '<undefined>' in the List-Unsubscribe header within Gmail can arise from a multitude of issues, ranging from potential bugs or updates on Gmail's end to problems with the sender's email configuration and coding. These issues include improperly formatted headers, encoding errors, failures in dynamic content generation, server-side errors, DNS propagation problems, transient network issues, non-compliant sending server configurations, and a lack of proper error handling. It might also be specific to certain email addresses or Google Workspace accounts.

Key findings

  • Potential Gmail Bug: The problem might stem from a recent update or bug within Gmail causing temporary parsing glitches.
  • Header Format Errors: Missing or incorrectly formatted List-Unsubscribe headers can result in Gmail displaying '<undefined>'.
  • Encoding Issues: Improper MIME encoding or the presence of unencoded characters can lead to parsing problems.
  • Dynamic Content Generation Failures: Problems during dynamic content generation in the sender's email system can lead to the unsubscribe link not being generated properly.
  • Server-Side and ESP Configuration: Configuration problems or non-compliance with modern email standards on the sending server and ESP can cause incorrect header generation.
  • Transient Errors: Transient network errors or temporary unavailability of the unsubscribe endpoint may contribute to the issue.
  • Domain Propagation: It is possible domain DNS is not propagated fully causing the issue

Key considerations

  • Check Gmail Status: Monitor Gmail for updates or known issues that might be causing parsing errors.
  • Review and Validate Header Format: Ensure the List-Unsubscribe header is correctly formatted according to RFC 2369 and RFC 8058 specifications, and contains a valid URL.
  • Ensure Correct Encoding: Verify correct MIME encoding, and ensure all special characters are properly encoded according to RFC 5322.
  • Examine Server-Side Logic: Review the server-side code responsible for generating the unsubscribe link to ensure it's correctly populated under all conditions.
  • Implement Error Handling: Implement robust error handling to manage situations where the unsubscribe URL cannot be created, and avoid defaulting to '<undefined>'.
  • Validate Rendering: Use email testing tools to validate unsubscribe URL rendering across different email clients and identify any inconsistencies.
  • Server and ESP compliance: Review sending server config for compliance to standards and that the ESP is up to date.

What email marketers say
8Marketer opinions

The appearance of '<undefined>' in the List-Unsubscribe header in Gmail can stem from multiple factors. These include: issues with Gmail's processing due to updates or bugs, problems with the sender's email system generating the header (such as server-side errors, incorrect formatting, or conditional logic failures), or a lack of proper error handling when an unsubscribe URL cannot be created. It may also be specific to certain email addresses or Google Workspace accounts.

Key opinions

  • Gmail Issues: Recent updates or temporary glitches within Gmail might cause incorrect header parsing.
  • Server-Side Errors: Errors in the sender's server-side code could lead to the unsubscribe link not being generated correctly.
  • Formatting Errors: Incorrectly formatted or missing List-Unsubscribe headers can result in Gmail displaying '<undefined>'.
  • Conditional Logic: The unsubscribe URL might not be populated under certain conditions in the sender's email sending code.
  • Error Handling: Lack of appropriate error handling or fallback mechanisms when an unsubscribe URL cannot be created.
  • Account Specificity: The issue might be specific to certain Gmail addresses or Google Workspace accounts.

Key considerations

  • Check Server Logs: Review server logs for errors related to the generation of the List-Unsubscribe header.
  • Validate Header Format: Ensure the List-Unsubscribe header is present and contains a valid URL, conforming to RFC specifications.
  • Review Sending Code: Check the email sending code to ensure the unsubscribe URL is always correctly populated under all conditions.
  • Implement Fallbacks: Implement error handling and fallback mechanisms to manage situations where the unsubscribe URL cannot be created.
  • Test Rendering: Use tools like Litmus or Email on Acid to validate unsubscribe URL rendering across different email clients.
  • Check for Gmail Updates: Be aware of updates or changes on Gmail's end that could be causing temporary parsing issues.
Marketer view

Email marketer from StackExchange explains that the server might be incorrectly setting the header based on a condition that isn't being met. Check the logic in your email sending code to verify that the unsubscribe URL is always correctly populated under all conditions.

June 2024 - StackExchange
Marketer view

Email marketer from Quora shares that problems can arise from poorly tested or non-existent fallbacks when the unsubscribe URL isn't available. Ensure that you have a system to handle and log cases where the URL cannot be created, rather than defaulting to '<undefined>'.

December 2022 - Quora
Marketer view

Email marketer from Gmass Blog explains that a missing or incorrectly formatted List-Unsubscribe header can cause this issue. Ensure the header is present and contains a valid URL.

June 2023 - Gmass Blog
Marketer view

Email marketer from Reddit suggests that the issue could be due to a recent update or change on Gmail's end causing a temporary glitch in header parsing. Wait and see if it resolves itself.

September 2024 - Reddit
Marketer view

Email marketer from Neil Patel Digital explains that the '<undefined>' value might be due to a server-side error generating the unsubscribe link. Check server logs for errors related to header generation.

November 2022 - Neil Patel Digital
Marketer view

Email marketer from Email Geeks confirms the issue persists and believes it must be a bug on Google's end, especially since no changes were made to their list-unsubscribe process.

December 2021 - Email Geeks
Marketer view

Email marketer from Email Marketing Forum explains that you should validate your unsubscribe URL generation using a tool like Litmus or Email on Acid to catch rendering issues before sending. These tools can highlight inconsistencies across different email clients.

March 2023 - Email Marketing Forum
Marketer view

Email marketer from Email Geeks shares that they are seeing issues with Gmail and list-unsubscribe, where the list-unsubscribe URL appears as '&lt;undefined&gt;' in the header for a specific sender. This issue seems to resolve itself, with the URLs appearing correctly later. The issue appears more consistently in Google Workspace accounts and may be specific to the receiving email address.

June 2022 - Email Geeks

What the experts say
3Expert opinions

The appearance of '<undefined>' in Gmail's List-Unsubscribe header points to a bug either in the sender's email system or on Google's end. Dynamic content generation issues, rendering errors in email templates, or a general failure in the software creating the email can lead to this problem. Robust error handling and continuous monitoring of the email system are essential to prevent and address these issues.

Key opinions

  • Bugs Identified: The '<undefined>' value indicates a bug somewhere in the email processing pipeline.
  • Dynamic Content Issues: Problems during dynamic content generation can cause the unsubscribe link to fail and display '<undefined>'.
  • Rendering Errors: Errors in the email template rendering process can lead to the unsubscribe link not being properly generated.
  • Google's End: Issue could be a bug with Googles end - but more likely its the sending server.

Key considerations

  • Check System: Check your sending system to ensure the unsubscribe link is correctly generated.
  • Implement Error Handling: Implement error handling to prevent problems such as '<undefined>' from appearing when generating an email.
  • Monitor Software: Continuously monitor the software that constructs the email to catch bugs.
  • Review Email Template: Review your email template, is a valid unsubscribe link being generated in code.
Expert view

Expert from Word to the Wise explains that seeing '<undefined>' in a List-Unsubscribe header could mean the system generating the email template has encountered an error during the rendering of the unsubscribe link. The system should be checked to ensure that the unsubscribe link is always properly generated and that proper error handling is in place to prevent such issues.

October 2021 - Word to the Wise
Expert view

Expert from Email Geeks states that seeing “undefined” in the list-unsubscribe header indicates a bug somewhere. While the focus should primarily be on the sender's message composition pipeline, the fact that it changes suggests there may be a bug on Google's end.

October 2023 - Email Geeks
Expert view

Expert from Spam Resource explains that one possible cause for an undefined List-Unsubscribe header is issues with dynamic content generation. If the email system fails to generate the unsubscribe link properly, it could result in the '<undefined>' value being inserted. This usually points to a bug or failure in the software that constructs the email.

December 2021 - Spam Resource

What the documentation says
6Technical articles

The '<undefined>' issue in Gmail's List-Unsubscribe header can be attributed to several technical factors related to header formatting, encoding, network issues, DNS problems, and server configurations. Ensuring compliance with RFC specifications, proper MIME encoding, error handling for transient issues, correct DNS settings, and an up-to-date sending server are crucial for resolving this problem.

Key findings

  • Format Compliance: Issues are often related to the List-Unsubscribe header not conforming to RFC 2369 and RFC 8058 specifications.
  • Encoding Problems: Improper encoding of special characters in the header can lead to parsing issues. Refer to RFC 5322 for encoding rules.
  • Transient Network Errors: Temporary unavailability of the unsubscribe endpoint or network errors can cause the issue.
  • MIME Encoding: Incorrect MIME encoding or improperly set content-type headers may be the cause.
  • DNS Propagation: DNS propagation issues can prevent the header from updating correctly across different servers.
  • Server Configuration: Non-compliant sending server configurations can result in incorrect header generation.

Key considerations

  • Adhere to RFC: Ensure the List-Unsubscribe header conforms to RFC 2369 and RFC 8058 specifications.
  • Proper Encoding: Ensure correct encoding of special characters and proper setting of the content-type header.
  • Implement Error Handling: Implement error handling to retry sending the header in case of transient network errors.
  • Verify DNS: Verify DNS settings and allow sufficient time for propagation.
  • Update Server: Ensure your sending server and ESP are up-to-date and correctly configured to comply with modern email standards.
Technical article

Documentation from MxToolbox advises that it is possible your domain may be experiencing DNS propagation issues. The header may not be correctly updating across different servers. Verify DNS settings and allow sufficient time for propagation.

September 2021 - MxToolbox
Technical article

Documentation from Microsoft Learn explains that transient network errors or temporary unavailability of the unsubscribe endpoint could cause this issue. Implement error handling to retry sending the header if it initially fails.

June 2023 - Microsoft Learn
Technical article

Documentation from Google Developers specifies that issues with the List-Unsubscribe header are usually related to the format. Ensure it conforms to RFC 2369 and RFC 8058 specifications. Incorrect format can result in the header being unreadable by email clients.

July 2024 - Google Developers
Technical article

Documentation from IETF suggests the issue could stem from incorrect MIME encoding. Ensure that you correctly encode any special characters and that the content-type header is correctly set to specify the encoding type.

March 2021 - IETF
Technical article

Documentation from RFC Editor specifies that the List-Unsubscribe header must be properly encoded. Ensure that the header does not contain any unencoded characters that could cause parsing issues. Refer to RFC 5322 for detailed encoding rules.

April 2024 - RFC Editor
Technical article

Documentation from Sparkpost notes that if the sending server's configuration is not compliant with modern email standards, it may result in incorrect header generation. Ensure your sending server and ESP are up to date and correctly configured.

June 2021 - Sparkpost

Related resources
2Resources

Long header folding adds additional spaces · Issue #1525 ...
Long header folding adds additional spaces · Issue #1525 ...

If sending a long header without spaces, header folding is incorrectly. Headers should fold with a CRLF, but after folding the CRLF is replaced with a LF and a space is introduced: $encoded = trim(...

GitHub
Workflow gives null in real run but works fine in test run - Questions ...
Workflow gives null in real run but works fine in test run - Questions ...

I’m using n8n self hosted on docker and a Gmail trigger I’m transforming the date like this {{ DateTime.fromFormat( $json.date, "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'").toFormat("yyyyMMdd") }} and inserting it into a contacts notes field it works completely fine during testing and then I put it live and an email came through. The resulting contacts had “null” instead of the date “20240229” so I went back into the workflow and ran the same node in test mode picking up the same email and it created th...

n8n Community

Related questions