Why are email engagement rates decreasing due to List-Unsubscribe header behavior and segmented email preferences?
Michael Ko
Co-founder & CEO, Suped
Published 1 Jul 2025
Updated 18 Aug 2025
7 min read
Email engagement rates can sometimes feel like a moving target. Just when you think you have a handle on what resonates with your audience, you might notice a subtle softening in performance. Recently, I’ve seen discussions around how the List-Unsubscribe header, coupled with how email preference centers are managed, can unexpectedly contribute to this decline, even leading to penalties from major inbox providers like Gmail and Yahoo.
The challenge often stems from a mismatch between user expectations and how email service providers (ESPs) handle unsubscribe requests initiated through these technical headers. It’s a nuanced area where compliance with the letter of the law might not always align with the spirit of user experience, potentially pushing otherwise engaged subscribers to mark your emails as spam, which directly impacts your sender reputation and deliverability.
The List-Unsubscribe header and user expectations
The List-Unsubscribe header is a crucial element for good email hygiene and deliverability. It allows recipients to easily unsubscribe from your emails directly from their email client, without having to find a link within the email body. This is mandated by major mailbox providers, and including it is a best practice. It’s designed to reduce spam complaints, as users are given a clear path to opt out instead of hitting the spam button.
The issue arises when an ESP’s implementation of this header is tied only to individual preference lists, rather than a global unsubscribe. If a user clicks the unsubscribe button in their email client, they typically expect to stop receiving all non-transactional emails from your brand. However, if that action only unsubscribes them from one specific list within a larger preference center, and they continue to receive other types of emails, it can lead to frustration.
Mailbox providers closely monitor unsubscribe behavior. If they see that users are requesting to unsubscribe via the List-Unsubscribe header but continue to receive mail, they may interpret this as you not honoring unsubscribe requests. This can then lead to your emails being directed to the spam folder, even for legitimate subscribers, causing a significant drop in engagement rates. This scenario often results in an increase in actual spam complaints, which further damages your sender reputation.
The list-unsubscribe header
A standard List-Unsubscribe header looks like this. It can include both a mailto link for direct unsubscribe and an HTTP link for a preference page, typically following RFC 8058 standards. However, the critical part is ensuring the action taken aligns with user expectations.
In fact, the perceived belief that providing an easy unsubscribe option decreases engagement is often a misconception. It actually protects your sender reputation and keeps subscribers happier by giving them control.
The impact of misaligned preferences on engagement
Email segmentation is crucial for sending relevant content to your audience. The idea is to group subscribers based on shared characteristics, behaviors, or preferences, allowing for more targeted campaigns. When done correctly, this leads to higher open rates and click-through rates because recipients receive content that genuinely interests them.
However, the problem arises when preference centers, despite offering granular control, aren't aligned with the broad expectation of the List-Unsubscribe header. If a user unsubscribes from a newsletter using the in-app option provided by Google or AOL, they don't see an option to select preferences. They just click Unsubscribe. If this action only removes them from one segment, but they still receive emails from other segments, it creates a negative user experience. This can lead to increased spam complaints, which will negatively impact your open rates and sender reputation.
The expectation from mailbox providers is that when a user clicks the List-Unsubscribe header, it should result in a broad unsubscribe, ideally from all non-transactional communications. If your ESP’s default behavior doesn’t allow for this, you may face penalties, regardless of whether you’re technically compliant with other regulations like CAN-SPAM, which only requires *an* unsubscribe option, not necessarily a global one via the header.
This situation can explain why engagement rates might be dropping, even if your deliverability numbers seem okay otherwise. It’s not necessarily that your emails are going to spam outright, but rather that users who thought they unsubscribed are now marking your subsequent emails as spam because they still receive content they no longer want. This feedback loop can hurt your overall standing with mailbox providers, leading to a poorer inbox placement.
Misaligned unsubscribe behavior
User expectation: When a user clicks the one-click unsubscribe button provided by Outlook or other email clients, they expect to stop receiving all marketing emails.
ESP behavior: The ESP processes the List-Unsubscribe request, but only removes the recipient from the specific list or segment associated with that particular email, not globally.
Consequence: The user receives more emails from other preferences, gets annoyed, and then marks these as spam, leading to higher spam complaint rates and poorer deliverability.
Effective unsubscribe management
User expectation: Users appreciate a clear and easy way to stop unwanted emails.
ESP behavior: The ESP is configured to process List-Unsubscribe requests as a global unsubscribe for all non-transactional mail.
Benefit: Reduced spam complaints, improved sender reputation, and better inbox placement across all campaigns. This strengthens your overall email program.
Strategies for effective segmentation and unsubscribe management
To mitigate decreasing email engagement rates, you need to align your unsubscribe mechanisms with user expectations and mailbox provider requirements. One key strategy is to ensure that your List-Unsubscribe header, especially the one-click unsubscribe functionality, provides a clear path to a global unsubscribe from all marketing communications. While it’s good to offer a preference center, the one-click option should serve as a broad opt-out.
If your ESP does not allow for a global unsubscribe via the List-Unsubscribe header by default, consider using unique `From` email addresses or even separate subdomains for different types of email content, such as marketing, product updates, or educational content. This helps mailbox providers differentiate between your sending types and can improve how they handle unsubscribe requests. For example, use marketing@yourdomain.com for promotional emails and updates@yourdomain.com for product news.
Additionally, regularly review your email list segmentation to ensure that your content remains highly relevant. Outdated or poorly segmented lists can lead to disengagement, even without explicit unsubscribe actions. Cleaning your email list and re-engaging inactive subscribers can also help maintain a healthy sending reputation. You can also explore how your List-Unsubscribe requests are increasing with Gmail to proactively address issues.
Remember, the goal is to provide a seamless and intuitive unsubscribe experience. When users feel they have control and their preferences are truly honored, they are less likely to resort to marking your emails as spam, which protects your deliverability and overall engagement. It's about prioritizing the user's journey over rigid technical adherence.
Views from the trenches
Best practices
Ensure your List-Unsubscribe header initiates a global unsubscribe from all non-transactional emails to align with user expectations and mailbox provider requirements.
Use distinct 'From' email addresses or subdomains for different types of email content to help mailbox providers understand your sending patterns and handle unsubscribes appropriately.
Segment your email lists effectively to ensure recipients receive highly relevant content, reducing the likelihood of disengagement and spam complaints.
Regularly clean your email lists by removing inactive or unengaged subscribers to maintain a healthy sender reputation and improve overall deliverability.
Always include a prominent, easy-to-find unsubscribe link within the email body, in addition to the List-Unsubscribe header, for user convenience.
Common pitfalls
Tying the List-Unsubscribe header solely to individual preference lists without offering a global opt-out, leading to user frustration and increased spam complaints.
Failing to monitor spam complaint rates and treating a 'not honoring unsubscribes' flag from providers as merely a suggestion, ignoring its impact on deliverability.
Continuing to send emails to users who have unsubscribed, even if from a different list, causing them to mark your messages as spam.
Not warming up new subdomains or dedicated IP addresses properly when diversifying sending infrastructure, which can temporarily hurt deliverability.
Over-relying on internal preference centers without considering how mailbox providers' in-app unsubscribe features function and what users expect from them.
Expert tips
If your ESP's default List-Unsubscribe behavior is too narrow, explore custom automations or workflows that trigger a global unsubscribe upon an in-app unsubscribe request.
Implement DMARC with a monitoring policy to gain insights into how mailbox providers are handling your emails, including potential spam complaints from non-compliance.
Prioritize user experience by designing an unsubscribe process that is intuitive and clear, allowing subscribers to easily opt-out fully or manage preferences without confusion.
Regularly test your unsubscribe links and List-Unsubscribe header functionality to ensure they are working as intended and providing the expected outcome for recipients.
Consider engaging with a deliverability consultant to audit your email program and identify hidden issues related to unsubscribe management and list hygiene.
Marketer view
Marketer from Email Geeks says that if an ESP links the List-Unsubscribe header to individual preferences, and the user unsubscribes from one, they might still get emails from other preferences, leading to spam complaints.
2024-05-07 - Email Geeks
Marketer view
Marketer from Email Geeks says a decrease in engagement can result from increased spam folder placement, which is often due to an increase in spam complaints, as Gmail does not suppress complainers, sending mail to their spam folder where opens are unlikely.
2024-05-07 - Email Geeks
Improving email engagement
Navigating the complexities of email deliverability requires a deep understanding of not just technical standards, but also user behavior and mailbox provider expectations. Decreasing engagement rates, even with high deliverability, can often be traced back to subtle misalignments, particularly concerning unsubscribe mechanisms and preference management. The List-Unsubscribe header is a powerful tool designed to protect your sender reputation by offering an easy opt-out.
However, if its implementation in your email program (especially via your ESP) leads to a partial unsubscribe when a user expects a global one, it will inevitably lead to frustrated subscribers marking your emails as spam. This negative feedback loop severely impacts your sender reputation and inbox placement. By prioritizing the user’s experience and ensuring that one-click unsubscribes lead to a comprehensive opt-out, you can maintain healthy engagement rates and avoid being added to a blocklist (or blacklist).
Gmail 
and Yahoo.
Google 
or AOL, they don't see an option to select preferences. They just click Unsubscribe. If this action only removes them from one segment, but they still receive emails from other segments, it creates a negative user experience. This can lead to increased spam complaints, which will negatively impact your open rates and sender reputation.
Outlook or other email clients, they expect to stop receiving all marketing emails.
