Some mailbox providers such as Google and Yahoo! will sometimes obscure engagement information, eliminating the ability for senders to collect user-level data. Image proxies are the image caches used by some mailbox providers that prevent Everest from providing data past the initial open. In these instances, the provider will store a copy of the tracking pixel on their server. Later views of the email will load your tracking pixel from their server rather than the original server.
Engagement
