Summary
Synchronizing unsubscribes during ESP migration involves a variety of approaches, ranging from leveraging built-in ESP features like webhooks and APIs to creating custom solutions with centralized databases and processing systems. Key strategies include utilizing master subscriber lists, List-Unsubscribe headers, feedback loops, and API integrations. Low-tech solutions, such as using email addresses as unsubscribe links, can serve as temporary workarounds. Ultimately, the goal is to maintain a clean email list, ensure compliance, and avoid deliverability issues by accurately reflecting unsubscribe preferences across all platforms.
Key findings
- Centralized Management: A central unsubscribe management system is critical, facilitating the receipt and processing of requests from all ESPs for consistent list updates.
- API Integration is Key: APIs enable real-time synchronization of unsubscribe data, ensuring accuracy and consistency across platforms.
- Leverage ESP Features: ESPs provide built-in mechanisms like webhooks, global unsubscribe groups, and bounce/complaint handling to aid in unsubscribe management.
- List-Unsubscribe Headers: List-Unsubscribe headers streamline the unsubscribe process, enhancing user experience and allowing for easier central management.
- Feedback Loops (FBLs): FBLs can be utilized to track unsubscribe requests, providing valuable data for synchronization and compliance.
Key considerations
- Implementation Complexity: Balance the complexity of custom solutions with available resources and the capabilities of the ESPs being used.
- Timeliness of Sync: Ensure timely synchronization to prevent sending emails to users who have already unsubscribed.
- Data Accuracy and Consistency: Implement measures to ensure accuracy across all systems, as data integrity is paramount.
- ESP Compliance: Understand and adhere to the email sending guidelines of major ISPs and ESPs to avoid penalties like automatic unsubscribes.
- Maintenance Overhead: Consider long-term maintenance and scalability when choosing a synchronization approach, especially for custom solutions.
- API Rate Limits: Be mindful of API rate limits when synchronizing via API to avoid service disruptions and missed updates.
What email marketers say
8 marketer opinions
Synchronizing unsubscribes between two ESPs during migration is crucial for maintaining a clean email list and avoiding deliverability issues. Common strategies include utilizing a master subscriber list, implementing a central unsubscribe management system with API integrations, using List-Unsubscribe headers, leveraging webhooks, and considering low-tech alternatives like replacing unsubscribe links with email addresses. Regularly cleaning the email list and ensuring a double opt-in process also helps.
Key opinions
- Centralized System: A central unsubscribe management system is critical for receiving and processing unsubscribe requests from all ESPs, updating all lists promptly to maintain consistency.
- API Integration: Using APIs to synchronize unsubscribe data between ESPs allows for real-time updates, ensuring that unsubscribes are consistently reflected across all platforms.
- List-Unsubscribe Headers: List-Unsubscribe headers enable recipients to unsubscribe directly from their email client, simplifying the process and improving user experience.
- Master Subscriber List: Maintaining a master subscriber list on one ESP and syncing it with others provides a single source of truth for subscription data.
- Shared Database: Implementing a shared database for unsubscribes, accessible via API by all ESPs, centralizes the management of subscription preferences.
Key considerations
- Timeliness: Ensure timely synchronization of unsubscribe data between ESPs to avoid sending emails to users who have opted out.
- ESP Capabilities: Consider the capabilities of each ESP, such as webhook support or API access, to determine the best synchronization method.
- Complexity: Balance the complexity of the synchronization solution with the resources available for implementation and maintenance.
- Data Accuracy: Implement measures to ensure the accuracy and consistency of unsubscribe data across all systems.
- Low-Tech Solutions: Evaluate low-tech alternatives like replacing unsubscribe links with email addresses as a simpler initial solution.
- List Cleaning: Maintain a healthy email list by implementing a double opt-in process and regularly removing inactive subscribers.
Marketer view
Email marketer from Litmus recommends using List-Unsubscribe headers. These headers allow recipients to unsubscribe directly from their email client, and the unsubscribes can be managed and propagated across different ESPs via a central system.
9 Oct 2023 - Litmus
Marketer view
Marketer from Email Geeks shares a solution involving a master subscriber list on ESP1, periodic syncing with ESP2 via API, and updating the master list based on unsubscribes from either platform. ESP2 needs to trigger something based on an unsubscribe, or use an unsubscribe notification email parse.
4 Sep 2023 - Email Geeks
What the experts say
3 expert opinions
Synchronizing unsubscribes between ESPs often involves leveraging backend APIs or list uploads/downloads for reliable data transfer, creating a centralized unsubscribe processing system accessible to all platforms via API, and utilizing feedback loops (FBLs) to track unsubscribe requests and synchronize the data across ESPs.
Key opinions
- Backend APIs/List Transfers: Using backend APIs or list upload/download processes is a reliable way to synchronize unsubscribe data, making error correction easier.
- Centralized Processing System: A centralized unsubscribe processing system provides a single point of management, ensuring all platforms are updated consistently.
- Feedback Loop Utilization: Implementing robust Feedback Loops (FBLs) and monitoring the data can effectively track unsubscribes and maintain synchronized lists.
Key considerations
- Reliability: Prioritize reliable methods like APIs to minimize errors during data transfer.
- Centralization Benefits: Evaluate the resources required to build and maintain a central unsubscribe processing system versus the benefits of simplified management.
- FBL Implementation: Assess the complexity of implementing and monitoring FBLs with various ISPs to effectively track and manage unsubscribes.
- Batch Processing Frequency: If using batch processing, decide on the optimal frequency to balance timeliness and resource usage.
Expert view
Expert from Word to the Wise suggests implementing robust Feedback Loops (FBLs) and utilizing them to track unsubscribe requests. Monitor FBL data from all participating ISPs, process the data to identify unsubscribed users, and then synchronize these updates across your ESPs.
6 Jul 2022 - Word to the Wise
Expert view
Expert from Email Geeks suggests synchronizing unsubscribes via backend APIs or list upload/download for reliability and easier error correction. Scripted batch processing a few times a day is recommended.
24 Jul 2022 - Email Geeks
What the documentation says
4 technical articles
Email service providers like Amazon SES, Mailgun, and SendGrid offer mechanisms to manage unsubscribes and maintain clean subscriber lists across multiple platforms. Amazon SES provides bounce and complaint handling, Mailgun offers webhooks for unsubscribe events, and SendGrid has a Global Unsubscribe Group with API access. Google emphasizes feedback loops and unsubscribe headers, with automatic unsubscribes for non-compliant senders.
Key findings
- Bounce and Complaint Handling: Amazon SES provides mechanisms for handling bounces and complaints, facilitating subscriber list maintenance.
- Webhooks for Unsubscribes: Mailgun offers webhooks that trigger on unsubscribe events, enabling real-time updates across platforms.
- Global Unsubscribe Group: SendGrid's Global Unsubscribe Group adds unsubscribed users to a suppression list accessible via API for list synchronization.
- Feedback Loops and Headers: Google emphasizes feedback loops and unsubscribe headers to improve email management and compliance.
Key considerations
- Notification Setup: Setting up notifications for bounces, complaints, and unsubscribes is essential for timely list updates.
- Real-Time vs. Batch Updates: Decide whether real-time updates via webhooks or periodic batch updates via API are more suitable for your needs.
- API Integration: Assess API capabilities and limitations for synchronizing suppression lists across different ESPs.
- Email Compliance: Ensure compliance with email guidelines to avoid automatic unsubscribes and maintain deliverability.
Technical article
Documentation from SendGrid explains that they offer a Global Unsubscribe Group that can be used to manage recipients. When a recipient unsubscribes from this group, their email address is added to a suppression list. The API can be used to keep multiple lists in sync.
21 Mar 2025 - SendGrid
Technical article
Documentation from Amazon Web Services explains that Amazon SES provides mechanisms for handling bounces and complaints, which can be used to maintain a clean subscriber list across different ESPs during migration. They recommend setting up notifications and using the data to update unsubscribe lists on both platforms.
22 May 2025 - Amazon Web Services
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