After months of news about Gmail’s tab feature and its impact on inbox placement, you probably thought it was time for a truce. But instead Gmail has launched a holiday offensive in their war on email marketers. This time they’re targeting image links and the impact could be major on open tracking and geo-targeting.

On or about December 3, Gmail began replacing links to images in emails with URLs to Google’s content serving network. The first time a recipient opens a linked image in one of your emails, Google appears to retrieve the image from your servers and cache it on their own for load requests from all subsequent recipients.

This doesn’t affect how recipients see images in your email. But it may have an impact on how well you can track their behavior.

Images used for open tracking have unique file names or query strings that need to be loaded on an individual basis. Google can’t cache these so the first load resulting in a tracking event should still be recorded. But subsequent reopens may not. Tracking of re-openers is very important in attribution models that see match customer behavior to purchases.

Geo-targeting may be also seriously disrupted. With their implementation of a proxy for image requests, Gmail appears to be masking the original IP address. As a result, location look-ups will show a central location – what appears to be the closest caching facility – instead of unique locations for each recipient.