How to control what's displayed on ISP unsubscribe link when List-ID is present?
Matthew Whittaker
Co-founder & CTO, Suped
Published 19 Apr 2025
Updated 19 Aug 2025
8 min read
Have you ever clicked an unsubscribe link provided by your email client, only to see a cryptic string like <10965567.xt.local> instead of a clear, readable name for the sender or list? It's a common frustration for email recipients, and a potential pitfall for senders aiming for optimal email deliverability and a positive user experience. This often happens when the List-ID header isn't configured with a friendly name.
This subtle detail in your email headers plays a significant role in how recipients perceive your brand and interact with your messages, particularly when they decide to opt out. A confusing unsubscribe option can lead to a negative impression or even a spam complaint, which can damage your sender reputation and lead to your emails being put on a blacklist (or blocklist).
Understanding and controlling what's displayed in the ISP-provided unsubscribe link, especially when a List-ID is present, is crucial for maintaining good email deliverability and fostering trust with your audience. Let's explore how these headers work and what steps you can take to ensure your unsubscribe experience is as clear and user-friendly as possible.
Understanding List-ID and List-Unsubscribe headers
At the heart of email list management and user experience are the List-ID and List-Unsubscribe email headers. The List-ID header, defined in RFC 2919, serves as a unique identifier for a mailing list. It helps email clients and mail servers categorize and manage incoming messages from specific lists. While primarily for machine readability, it can also contain a human-readable friendly name that can be displayed to the user.
The List-Unsubscribe header, detailed in RFC 2369, is what email clients use to provide an easy, often one-click, unsubscribe option within their user interface (UI). This header usually includes one or more ways to unsubscribe, typically a mailto: address and an http(s): URL. The List-Unsubscribe-Post header, defined in RFC 8058, specifically enables the one-click unsubscribe functionality, allowing users to opt out with a single action without visiting a landing page. This greatly improves user experience and can reduce spam complaints.
When both List-ID and List-Unsubscribe headers are present, email clients like Gmail or Outlook often prioritize displaying the List-ID value in the unsubscribe prompt. This means the text presented to the user for unsubscribing depends heavily on how you've formatted your List-ID header. If it's a friendly name, the user gets a clear choice. If it's an opaque string, they might be confused.
Example of well-formed List-ID and List-Unsubscribe headershttp
The core issue arises when the List-ID header, instead of containing a user-friendly name, holds a cryptic or machine-generated string. This is particularly common with various email service providers (ESPs) that automatically generate these identifiers. For example, some platforms might produce a List-ID that looks like <12345678.xt.local> or similar opaque values.
When an ISP (Internet Service Provider) or email client sees such a List-ID, it might display this exact string to the user next to the unsubscribe button. Imagine seeing Unsubscribe from <12345678.xt.local> instead of Unsubscribe from Delta Airlines Promotions. This can confuse recipients, making them less likely to use the legitimate unsubscribe option and more likely to mark your email as spam.
The negative consequences extend beyond user frustration. Higher spam complaint rates signal to ISPs that your emails are unwanted, potentially leading to deliverability issues and placement on a blocklist (or blacklist). Even if your List-Unsubscribe header itself is correctly configured for one-click unsubscribes, the off-putting List-ID display can undermine its effectiveness.
Cryptic List-ID Display
When your List-ID header contains only a technical string, like those generated by some ESPs (e.g., Salesforce Marketing Cloud or SparkPost), it can confuse users.
User experience: Recipients see an unidentifiable string, making them unsure what they are unsubscribing from. This can lead to frustration and distrust.
Spam complaints: If the unsubscribe option is unclear, recipients are more likely to hit the Report Spam button instead, directly harming your sender reputation and increasing the risk of your domain being put on a blocklist.
Friendly List-ID Display
When your List-ID header includes a descriptive, human-readable name, email clients can display this clearly to the user, like "Your Company Newsletter" <newsletter.yourdomain.com>.
User experience: Recipients instantly recognize the list, making the unsubscribe process straightforward and reassuring. This builds trust in your sending practices.
Spam complaints: A clear unsubscribe option leads to fewer spam reports, which positively impacts your domain's sending reputation and helps keep you off any email blocklist.
For senders using Salesforce Marketing Cloud (SFMC) specifically, the issue of an opaque List-ID displaying in the Gmail UI is a well-known challenge. This stems from how SFMC implemented the header, often resulting in an unreadable identifier. Unfortunately, there isn't an external fix, meaning senders typically need to work with their SFMC account representatives to provide feedback and advocate for improvements in how this header is managed.
Strategies to control the unsubscribe display
To gain control over what's displayed in the ISP unsubscribe link, you need to focus on correctly formatting your List-ID header. The key is to include a friendly part alongside the actual identifier. This friendly part is what email clients are designed to display to users. For example, instead of just <mailinglist.example.com>, you would use something like "My Company Newsletter" <newsletter.mycompany.com>.
Your email service provider plays a critical role here. Many ESPs offer the option to customize the List-ID header to include this friendly name. You might need to check your ESP's documentation, contact their support, or explore advanced settings to implement this change. If your ESP does not provide this flexibility, it might be a factor to consider in your choice of email platform.
Beyond the List-ID, ensure your List-Unsubscribe header is correctly configured, especially for one-click unsubscribe using the List-Unsubscribe-Post header. This is a critical factor for user convenience and for meeting Google's and Yahoo's new sender requirements. A functional and clear unsubscribe process is a strong signal to ISPs that you are a legitimate sender. For more details on how email clients handle these headers, you can read our guide on how email clients generate unsubscribe links.
Action plan for a clear unsubscribe display
Check your ESP's documentation: Look for options related to List-ID and List-Unsubscribe customization.
Implement a friendly name: Ensure your List-ID header includes a clear, recognizable name for your list.
Verify one-click unsubscribe: Confirm that your List-Unsubscribe-Post header is correctly implemented to allow for easy one-click opt-outs. This is vital for maintaining a good sender reputation.
Monitor and test: Send test emails to various clients (e.g., Gmail, Yahoo, Apple Mail, Outlook) to ensure the unsubscribe link displays as intended. You can verify your headers using an email deliverability testing tool. If the link is not showing up, you may need to troubleshoot why the Gmail List-Unsubscribe link is not showing.
Impact on deliverability and user trust
A clear and functional unsubscribe process is not just a courtesy; it's a critical component of healthy email deliverability. When recipients can easily opt out from your mailings, they are far less likely to mark your emails as spam. Spam complaints are one of the most damaging signals to ISPs, directly impacting your sender reputation and increasing the likelihood of your messages landing in the spam folder, or even being blocked entirely, possibly leading to your domain being put on a blocklist.
By ensuring your List-ID and List-Unsubscribe headers are properly configured with friendly, readable names, you contribute significantly to a positive user experience. This builds trust with your audience, reinforces your brand's professionalism, and encourages them to use the intended unsubscribe mechanism rather than resorting to spam reports. It aligns with best practices for overall email marketing health and compliance, particularly with new sender requirements for Google and Yahoo.
Ultimately, clear communication at every touchpoint, including the unsubscribe process, is paramount. Investing in the correct configuration of these technical headers translates directly into improved inbox placement and a stronger, more reliable email program. This proactive approach helps prevent email deliverability issues and ensures your legitimate messages reach your subscribers effectively.
Views from the trenches
Best practices
Always use a human-readable friendly name in your List-ID header.
Prioritize one-click unsubscribe functionality via List-Unsubscribe-Post.
Regularly test unsubscribe links in various email clients for consistent display.
Integrate a clear in-body unsubscribe link to complement header-based options.
Common pitfalls
Relying on opaque List-ID strings that confuse recipients.
Not implementing one-click unsubscribe, increasing spam complaints.
Directing unsubscribes to complex pages requiring logins or multiple steps.
Failing to monitor deliverability metrics related to spam complaints.
Expert tips
Advocate with your ESP for flexible List-ID configuration options.
Analyze DMARC reports for insights into user engagement and potential unsubscribe issues.
Consider how List-ID might be used by advanced email clients for sorting.
Ensure consistency in branding across all unsubscribe touchpoints.
Marketer view
Marketer from Email Geeks says ISPs sometimes prioritize the List-ID over List-Unsubscribe header details for display.
2023-12-02 - Email Geeks
Expert view
Expert from Email Geeks says that while the List-ID is a list identifier, its presentation can appear poor when it is an opaque string from a platform.
2023-12-02 - Email Geeks
Keys to a successful unsubscribe experience
Ensuring a clear and recognizable unsubscribe link in ISP interfaces is more than a technical detail; it's a fundamental aspect of maintaining a healthy email program and positive sender reputation. By correctly configuring your List-ID with a friendly name and implementing robust List-Unsubscribe headers, you empower your subscribers to manage their preferences easily. This reduces the likelihood of spam complaints and helps your emails consistently reach the inbox.
Proactive monitoring and testing of your email headers across different clients are crucial to confirm that your efforts are paying off. A transparent unsubscribe process builds trust, enhances your brand's image, and contributes significantly to your overall email deliverability success. Prioritize this often-overlooked aspect of email sending to maintain a strong relationship with your audience and avoid the pitfalls of low engagement and potential blacklisting.
Gmail or 
Outlook often prioritize displaying the List-ID value in the unsubscribe prompt. This means the text presented to the user for unsubscribing depends heavily on how you've formatted your List-ID header. If it's a friendly name, the user gets a clear choice. If it's an opaque string, they might be confused.
Salesforce Marketing Cloud or 
SparkPost), it can confuse users.
Google's
and Yahoo's new sender requirements. A functional and clear unsubscribe process is a strong signal to ISPs that you are a legitimate sender. For more details on how email clients handle these headers, you can read our guide on how email clients generate unsubscribe links.
, Apple Mail
