Google Quietly Updates Gmail to Cache Images shock for Email Marketers

 Email messages are, by and large, attractive static. Once they're sent, they're fixed. The one exception is the images, which are downloaded when the  receiver reads the message. 

As that happens, a treasure trove of information is shared with the image host. Many innovative companies including ESPs, MovableInk, ReturnPath, Litmus and AudiencePoint use that data in a selection of ways.

By switching to caching the images, Google has caused that source of information to largely dry up.

There are six pieces of information that marketers often rely on that the Google cache impacts:

1. spot

The Google cache hides the source Internet Protocol (IP) address of the reader. That address can be used to decide the location of the reader. Gmail users now all appear to reside in Google datacenters.

Often, this is used for nothing more than sketch pretty maps showing readership around the world. But some companies also use it to provide more embattled information, like an image with the address of the outlet that is closest to you right now.

2. Referrer

The referrer indicates what requested the image be downloaded. This data is greatly used by reports that tell you which folder your email ended up in and how many recipients were using the Gmail web line versus a native client or the mobile app.

3. Browser

The user-agent string tells a site a lot about the program that is downloading the image. Browser account, operating system and device are often deduced from this. The impact of not having this is two-fold.

Statistics on email client and device usage will be engaged for Gmail users, but also any tool that customizes images for the audience will be unable to function properly. So delivering a mobile-optimized image for a mobile device versus a desktop will not be practical.

4. Cookies

Cookie synchronization for ad serving and retargeting may be undermined. Advertisers are increasingly performing cookie synchronization between ad data management platforms and their CRM databases. The advantage is more relevant ad targeting and more timely and relevant email. Gmail may become a black hole for this action.

5. Timing

Tools that deliver images enthusiastically based on time will be negatively impacted. Once the recipient sees the image, it will not be downloaded again and so will not be able to change.

6. Counts

Since images are cached they will, at most, be downloaded once per receiver. Total opens will fall. Tools that use multiple image downloads to infer read times and repeat reading will be negatively impacted.

One other impact of the Google image cache is that it restricts images to 10MB. Any image larger than that produces an error. While not an problem for most, this can be significant for active images.

If you're wondering why Google would make these changes, I can think of a pair of reasons.

The first is privacy. Unlike most other webmail providers, Google has always hidden the submitting IP address of emails. This change also masks the IP address of readers, as well as other information about them that might be considered .

The second is performance. Google's cache service is fast, but some senders' image delivery isn't. This can give a better experience for Gmail users.

There are other possible reasons, but most of them require ownership of a tin-foil hat so I won't get into them right now.

The larger impact though is if you're delivering images enthusiastically based on device, time or location. In these instances, you will certainly need to make changes. The most likely outcome is that Gmail users will get a degraded knowledge, rather than the improved experience Google was aiming for.

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