Opens tracking on email

Email open tracking is typically done using a technique called a tracking pixel. This is a small, invisible image that is embedded in the email. When the email is opened, the image is downloaded from the server, and the server logs this as an "open" event.

However, as you've discovered, some email clients like Google Gmail and Microsoft Outlook cache images, which can interfere with open tracking. Once the image is cached, subsequent opens of the email will load the image from the cache instead of downloading it from the server, so the server won't see these as additional "opens".

To get around this, you could try generating a unique URL for the tracking pixel for each email. This would prevent the email client from caching the image, because each URL would be different. However, this would require a server-side component to generate the unique URLs and serve the images.

Here's a basic example of how you might do this:

• When sending the email, generate a unique ID for the email (for example, a UUID).
• Embed a tracking pixel in the email with a URL like https://domain.com/track_open?id=YOUR_UNIQUE_ID.
• On your server, set up an endpoint at /track_open that takes an id parameter. When this endpoint is hit, log the id as an "open", then return the tracking pixel image.

This approach should allow you to track each open of the email, because each email will have a unique tracking pixel URL that won't be cached.

However, keep in mind that this technique may not work if the recipient's email client is set to not automatically download images, or if they are using an email client that doesn't support HTML emails. Also, some email clients or security software may block tracking pixels or warn the user about them, which could affect your open rates.

As for the HTML structure of the email, it's unlikely that this would have a significant impact on open tracking. The key factor is whether the tracking pixel is downloaded, which is primarily determined by the email client's image caching and download settings, not the structure of the HTML.