Why do I not receive a tracking message.opened webhook?

Sometimes, you might not receive message.opened webhook notifications when a recipient has read a message. This is a known limitation of pixel-based open tracking, and it's common across the email industry, not specific to Nylas.

How message open tracking works

Nylas detects that a message has been opened by embedding a transparent single-pixel image into the message's HTML. When a recipient opens the message, their email client makes a request to Nylas' servers to download the image. Nylas records that request as a message.opened event and sends a notification to your webhook endpoint.

Because this method relies on the recipient's email client requesting the image file from Nylas, anything that prevents that request will prevent the notification.

Why you might not receive message.opened notifications

Recipient-side privacy features

Many email providers and clients include privacy features that block or interfere with tracking pixels. These are outside of Nylas' control.

• Apple Mail Privacy Protection: Apple Mail can pre-fetch remote content (including tracking pixels) through a proxy at delivery time, or block them entirely. This may cause false positives (immediate opens) or no notification at all, depending on the recipient's settings.
• Gmail image proxy: Gmail routes all image requests through Google's proxy servers. While this generally still triggers open tracking, it can mask the recipient's actual IP address and user agent.
• Outlook privacy settings: Microsoft Outlook can be configured to block automatic image downloads by default. Unless the recipient manually loads images, the tracking pixel is never requested.
• Privacy-focused email providers: Providers like ProtonMail and Tutanota strip or proxy remote images by default to protect recipient privacy.

Email client behavior

• Text-only email clients: Some email clients render only plain text and do not load HTML content, so the tracking pixel is never downloaded.
• Clients that strip images: Some email clients strip image files from HTML messages or replace them with placeholder text (for example, <spacer.gif>).
• Clients that block remote content: Many email clients block remote images by default and require the recipient to click "Load images" manually.

Ad blockers and security software

• Browser-based ad blockers: Extensions like uBlock Origin or Adblock Plus can block tracking pixels in webmail interfaces (such as Gmail or Outlook on the web).
• Corporate email security gateways: Organizations often use email security solutions that strip tracking pixels, rewrite image URLs, or sandbox external content before delivery.
• Network-level filtering: Corporate firewalls, VPNs, or DNS-based ad blockers (such as Pi-hole) may block requests to tracking domains.

Configuration issues on your side

Before investigating recipient-side causes, verify your own setup:

• Webhook not subscribed to message.opened: Check that your webhook destination includes message.opened in its trigger_types. You can verify this in the Nylas Dashboard or via the Webhooks API.
• Open tracking not enabled on the message: Verify that you set tracking_options.opens to true in your Send Message request.
• Deleted grant: If the grant associated with the tracked message has been deleted, Nylas can no longer deliver tracking notifications. If a grant expires, re-authenticate it rather than deleting it to preserve tracking data. See Handling expired grants for details.
• Webhook endpoint issues: Ensure your webhook endpoint is reachable, returns a 200 response, and correctly handles the webhook challenge.

Solutions and workarounds

Because pixel-based open tracking is inherently unreliable, consider the following strategies:

Combine with link clicked tracking

Use Link Clicked tracking alongside open tracking. A link click is a stronger and more reliable signal of engagement because it requires an active action from the recipient and is not affected by image-blocking settings.

Resources

I received a webhook message.opened immediately or too many webhooks when using tracking

How to stop your emails from being tracked

Updated April 16, 2026 11:31