What are email image proxies (e.g., Gmail Image Proxy)?
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An email image proxy is a server that sits between the recipient and your email's images. Instead of your email client loading images directly from your ESP's servers, the proxy fetches them on behalf of the user and serves them from its own infrastructure.
The two you'll encounter most often: Gmail's Image Proxy (which routes image requests through Google's servers) and Apple's Mail Privacy Protection proxy (which goes a step further and prefetches images before the user even opens the email).
Why do they exist? Security and privacy. Loading images directly exposes the recipient's IP address and device information to whoever hosts those images. A proxy hides that information, routing the request through servers with anonymized or provider-owned IPs instead. It also lets the provider scan images for malicious content before displaying them.
The tradeoff for email marketers: proxies break location and device tracking. Your open tracking data will show Google or Apple IPs, not your subscriber's real location. Time-of-open data becomes less reliable. And with Apple's proxy in particular, the prefetch behavior means open rates are inflated because images load before users actually engage.
Gmail's proxy also caches images, which means later opens of the same email might not generate new pixel requests if the cache is still valid. This can lower your open count for re-opens and may affect A/B test timing.
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