Why am I receiving multiple 'message.opened' webhook notifications?

When sending an email, you may notice an immediate 'message.opened' webhook notification. However, you won't receive further 'message.opened' notifications from that recipient. This behavior is influenced by how email clients and CDNs handle image pixels used for tracking.

Observed Behavior

  1. CDN Caching: Content Delivery Networks (CDNs) cache the tracking image pixel across multiple proxies, leading to multiple reads.
  2. Gmail Image Caching: Gmail caches images as soon as they receive the email, triggering a 'message.opened' webhook notification immediately.
  3. Mass Email Opens: Opening one email can trigger the opening of other emails stored by that provider, resulting in multiple 'message.opened' notifications.
  4. Multiple Notifications: This can also lead to multiple 'message.opened' and 'message.link_clicked' notifications being recorded.


To manage this issue, disregard immediate (under a minute) responses and store the objects in a SET to eliminate duplicates. Be aware that tracking is becoming more challenging as browsers and email providers enhance privacy measures.


For more information, visit: Troubleshooting Immediate Webhook Notification


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