The Email Client Monitor pixel captures a more limited set of data for Web Proxy than for other platforms (Desktop, Mobile, Webmail, or Other). To understand why, let's look at how Web Proxy works.

How does Web Proxy work?

For security reasons, some mailbox providers, such as Gmail and Yahoo!, cache images from an email before serving those images to message recipients. The Email Client Monitor pixel is a transparent image, so it is also cached by the mailbox provider. Caching counts as turning on the image, so it causes the pixel to fire.

What information is captured and why?

If you receive subscriber-level data, you can see all information captured for "proxy" under the Platform column:

• Mailbox provider (Gmail, Yahoo!)
• Date and time the pixel fires, e.g., when the recipient opens the email

Other information captured by web proxy isn't useful, so it isn't recorded. For example, "location" would show wherever the Google server is located, not where the message recipient is when the message was opened.

Are there exceptions?

Occasionally a browser may bypass the caching behavior, for example by altering the user-agent string. If this happens, you may see a Gmail or Yahoo! open show up under Webmail instead of Web Proxy, with additional information such as location and device information attached.