Can spam filters trigger email unsubscribes and how to prevent it?

Summary

Spam filters can trigger unintended unsubscribes by following links in emails, including unsubscribe links, to verify validity. This is a widespread issue addressed through various preventative measures spanning from the initial subscription to the unsubscription process. Solutions include: implementing double opt-in for subscriptions; using confirmed opt-out processes requiring an extra click for unsubscription; adding CAPTCHAs or similar challenges on unsubscribe pages; and employing honeypot techniques to identify and filter out bots. Other recommendations include monitoring IP addresses for surges in unsubscribes, adding a delay to the unsubscribe process, using authentication like login or email verification before completing the unsubscription, and utilizing POST requests for list-unsubscribe headers. Maintaining clean lists and reducing spam complaints also helps indirectly mitigate the issue. RFC 8058 and RFC 2369 provide context for list unsubscribe headers.

Key findings

  • Double Opt-In: Using double opt-in helps ensure genuine subscribers, preventing bot sign-ups and subsequent unintended unsubscribes.
  • Confirmed Opt-Out: A confirmed opt-out process (requiring an extra click) prevents accidental or bot-triggered unsubscribes.
  • CAPTCHA/Challenges on Unsubscribe: CAPTCHAs or challenges on unsubscribe pages prevent automated systems from completing the process.
  • Honeypot Techniques: Honeypots (hidden links or fields) identify and filter out bots based on their interaction.
  • IP Monitoring: Monitoring IP addresses for unsubscribe surges can help identify bot activity.
  • Unsubscribe Delay: Adding a delay to the unsubscribe process allows for verification and potential intervention.
  • POST for List-Unsubscribe: Using POST requests for List-Unsubscribe headers helps prevent automated unsubscribes.
  • Authentication for Unsubscribe: Requiring login or email verification before unsubscribing prevents unauthorized actions.

Key considerations

  • Implementation Complexity: Some solutions, like honeypots, authentication, and POST request implementation, require technical expertise and monitoring.
  • User Experience Impact: Adding extra steps like CAPTCHAs and authentication can impact user experience and satisfaction.
  • Data Privacy: Logging IP addresses and requiring email verification require attention to data privacy and compliance.
  • Potential for False Positives: Honeypots might accidentally flag legitimate users; careful configuration is needed.
  • Maintenance and Monitoring: Many solutions require ongoing monitoring and adjustments to remain effective.
  • Industry-Wide Problem: The issue of spam filters triggering unsubscribes is a complex, industry-wide problem with no single, universally effective solution.

What email marketers say
10Marketer opinions

Spam filters can inadvertently trigger unsubscribes by following links in emails, including unsubscribe links, to verify email validity. This is a known issue addressed through various preventative measures. Solutions include implementing double opt-in for subscriptions, confirmed opt-out processes (requiring an extra click for unsubscription), CAPTCHAs or challenges on unsubscribe pages, and honeypot techniques to identify and filter out bots. Monitoring IP addresses for unsubscribe surges, adding a delay to the unsubscribe process, and using authentication methods like login or email verification are also recommended.

Key opinions

  • Double Opt-In: Using a double opt-in process for subscriptions helps ensure genuine interest and prevents bots from subscribing.
  • Confirmed Opt-Out: Implementing a confirmed opt-out process requires an extra step to confirm unsubscription, preventing accidental or bot-triggered unsubscribes.
  • CAPTCHA/Challenges: Using CAPTCHAs or similar challenges on unsubscribe pages can prevent automated systems from completing the unsubscription process.
  • Honeypot Techniques: Employing honeypot techniques, like hidden links, can identify and filter out bots based on their interaction with these traps.
  • IP Monitoring: Monitoring IP addresses for surges in unsubscribes can help identify if bots or spam filters are causing the issue.
  • Unsubscribe Delay: Adding a delay to the unsubscribe process can prevent immediate removal, allowing for further verification or intervention.

Key considerations

  • Implementation Complexity: Some methods, like honeypots or authentication, may require more technical implementation and monitoring.
  • User Experience: Adding extra steps to the unsubscribe process, like CAPTCHAs, might impact user experience and satisfaction.
  • Data Privacy: Logging IP addresses requires careful consideration of data privacy regulations and user consent.
  • False Positives: Honeypot techniques might accidentally flag legitimate users as bots; careful configuration is needed.
  • Maintenance: Some techniques, such as IP monitoring, require continuous monitoring and potential adjustments to remain effective.
Marketer view

Email marketer from Litmus responds to the issue of bots clicking links. One of their solutions involves adding a honeypot link (a link invisible to humans) to your emails; bots will often click these links, and you can then filter out these bots from your data.

November 2022 - Litmus
Marketer view

Email marketer from Mailjet explains that you can add authentication to the unsubscribe process, such as requiring users to log in or verify their email address before completing the unsubscription. This prevents unauthorized unsubscribes by bots.

March 2023 - Mailjet
Marketer view

Email marketer from WebmasterWorld forum mentions they use a honeypot technique where they have a hidden field that, if populated, indicates a bot submission. This allows them to filter out bot-triggered unsubscribe requests.

May 2022 - WebmasterWorld
Marketer view

Marketer from Email Geeks shares that Gmail offers the ability to unsubscribe when a message is marked as spam, dependent on the list-unsubscribe header, and suggests other providers might do something similar.

February 2022 - Email Geeks
Marketer view

Email marketer from DigitalPoint forum explains the need for a confirmed opt-out process. The user has to actually click the link that confirms the unsubscription. Helps prevent false unsubscribes.

January 2024 - DigitalPoint
Marketer view

Email marketer from Reddit suggests adding a delay to the unsubscribe process. Don't remove the user immediately, rather add a task to a queue that runs a minute later.

June 2021 - Reddit
Marketer view

Email marketer from SendGrid explains that they advise using a double opt-in process to ensure that subscribers genuinely want to receive emails. This helps prevent bots and spam filters from triggering subscriptions, which can lead to unwanted unsubscribes later on.

June 2022 - SendGrid
Marketer view

Email marketer from StackOverflow suggests logging the IP address of the user when they unsubscribe. If there is a surge of unsubscribes from one IP, then this will help identify if it is a bot or spam filter that is causing it.

July 2021 - StackOverflow
Marketer view

Email marketer from Neil Patel's Blog explains that spam filters can sometimes trigger unsubscribes if they follow links in the email to check their validity, which can unintentionally trigger the unsubscribe link. To prevent this, implement a double opt-in process for subscriptions and use a confirmed opt-out process for unsubscribes, requiring an extra step to confirm the unsubscription.

February 2023 - Neil Patel's Blog
Marketer view

Email marketer from Email on Acid shares that spam filters clicking links and triggering unsubscribes is a known issue. Their recommendation is to implement a CAPTCHA or similar challenge on the unsubscribe page to prevent automated systems from completing the unsubscription process.

February 2023 - Email on Acid

What the experts say
5Expert opinions

Experts agree that spam filters can cause unintended unsubscribes, necessitating preventative measures. Requiring an extra click for unsubscription is a common solution. For list-unsubscribe headers, using a POST request instead of GET is recommended to prevent automated unsubscribes. Implementing CAPTCHAs before completing the unsubscribe action also prevents bot-triggered unsubscribes.

Key opinions

  • Two-Click Unsubscribe: Changing from a one-click to a two-click unsubscribe process is effective in preventing unintended unsubscribes.
  • POST vs. GET: Using POST requests for list-unsubscribe helps prevent automated unsubscribes, as GET requests should not alter data on the server.
  • CAPTCHA Implementation: Implementing a CAPTCHA before completing the unsubscribe process helps prevent bots from triggering unsubscribes.

Key considerations

  • Technical Implementation: Correctly implementing POST requests requires technical expertise.
  • User Experience: Adding extra steps like CAPTCHAs might negatively affect user experience.
  • Industry-Wide Issue: Spam filter unsubscribes are a known industry-wide problem with no single perfect solution.
Expert view

Expert from Word to the Wise recommends implementing a CAPTCHA before the unsubscribe action is completed, to prevent bots or automated systems from unsubscribing users unintentionally.

July 2024 - Word to the Wise
Expert view

Expert from Email Geeks shares their experience with spam filters causing unsubscribes and inflated clicks, noting it's an industry-wide issue. They now require an extra click for unsubscription.

September 2021 - Email Geeks
Expert view

Expert from Email Geeks, Laura Atkins, explains that POST is used to post a change and GET is used to read data. Alexander Zeh adds that GET should never alter data on the server, while POST is supposed to change something.

January 2025 - Email Geeks
Expert view

Expert from Email Geeks recommends changing "one click" unsubscribe to "two click" unsubscribe, regardless of method, and suggests that list-unsub should require POST for immediate unsubscribe.

December 2024 - Email Geeks
Expert view

Expert from Email Geeks initially explains that an unsubscribe link should not complete the unsubscribe if the link is followed, but then corrects themselves.

December 2024 - Email Geeks

What the documentation says
4Technical articles

RFC 8058 defines one-click unsubscribe via the List-Unsubscribe header, acknowledging potential abuse by automated systems and suggesting rate-limiting and confirmation steps. Google's documentation highlights the importance of maintaining a clean list and providing easy unsubscribe options to reduce spam complaints. Mailchimp recommends reCAPTCHA on signup forms to prevent bot subscriptions and minimize spam filter interaction. RFC 2369 defines the List-Unsubscribe header, explaining mechanisms that can be unintentionally triggered by filters.

Key findings

  • Rate Limiting and Confirmation: RFC 8058 suggests using rate limiting and confirmation steps to mitigate unintended unsubscribes triggered by automated systems.
  • List Hygiene: Maintaining a clean email list and providing easy unsubscribe options are important for minimizing spam complaints and improving deliverability.
  • reCAPTCHA for Signup: Implementing reCAPTCHA on signup forms helps prevent bots from subscribing to email lists.
  • List-Unsubscribe Header Mechanism: Understanding the List-Unsubscribe header mechanism (defined in RFC 2369) is essential for addressing unintended unsubscribes.

Key considerations

  • Implementation Complexity: Implementing rate-limiting, confirmation steps, and reCAPTCHA require technical expertise.
  • User Experience: Adding steps to the signup or unsubscribe process can potentially impact user experience and conversion rates.
  • Indirect Solutions: Some documented solutions address the issue indirectly by focusing on list hygiene and spam complaints.
Technical article

Documentation from datatracker.ietf.org explains that RFC 8058 defines a method for one-click unsubscribe via the List-Unsubscribe header, but also acknowledges the potential for abuse by automated systems. The RFC suggests implementations should consider rate-limiting and confirmation steps to mitigate unintended unsubscribes.

December 2022 - datatracker.ietf.org
Technical article

Documentation from Google explains that high spam complaint rates can negatively impact deliverability. Although it doesn't directly address bot-triggered unsubscribes, it highlights the importance of maintaining a clean list and providing easy, legitimate unsubscribe options to reduce spam complaints, which indirectly addresses the issue.

March 2022 - Google
Technical article

Documentation from RFC 2369 defines the List-Unsubscribe header, explaining how it enables users to easily unsubscribe from mailing lists. While it doesn't directly address spam filter unsubscribes, it's fundamental to understanding the mechanisms that can be unintentionally triggered by filters.

April 2022 - rfc-editor.org
Technical article

Documentation from Mailchimp explains that using reCAPTCHA on signup forms can prevent bots from subscribing to your email list, which can help to reduce spam filter interactions with your unsubscribe links later. They recommend this as a best practice for list hygiene.

December 2022 - Mailchimp