Gmail Image Caching

Wednesday, December 11, 2013 Listrak 0 Comments

On Friday December 6, 2013, it was reported that Google had made some changes to the Gmail infrastructure.  Apparently, starting on December 3rd, images are being served via a proxy for Gmail users.  This means that Gmail now saves image files from unique URLs temporarily and changes these URLs in emails so that they point to the cached images.  The user’s browser then loads and displays Gmail’s cached images.  This can cause problems for a number of reasons.  When Gmail loads images into the cache, the user’s device and geo information gets lost.  An open will now originate from a Mountain View, California with an IP address similar to  And the user agent, which normally holds the user’s device information, will now look like ‘Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv: Gecko/2009021910 Firefox/3.0.7 (via’.
This is not affecting Listrak open counts.  Since we do not track multiple opens, this change will not affect open rates for our clients.  The initial open is captured via our tracking pixel and clients can continue to rely on the reported open information they are seeing in the application.  Obviously the geo-location data will be incorrect as Gmail users will now appear to reside in Google’s datacenter.  Furthermore, this will also create an issue with data such as “Activity by Email Client” within Listrak as the reported user agent from Gmail will always be the same.  It should be noted that this does not appear to be affecting POP or IMAP mail clients, only web based Gmail users and perhaps the Gmail phone app (research is ongoing).  Testing was done with Apple’s iPhone email client and no caching was detected.   Changes to images after a send will also be affected.  From our testing, it appears Google will cache the images for 24 hours, however it is still a little early to tell if this will always be the case.
The important points to remember:
•  This is an industry-wide issue which is not isolated to the Listrak platform.
•  This does not affect tracking of the first email open as the cache fetches the image from the sender.
•  This does affect tracking if someone opens an email more than once as the email client is pulling images from the Google cache.
•  This does affect geo-location detection as Google is not providing any information about where the open happened, only their datacenter IP.
•  This does affect user agent detection as Google is not providing any information about the original user agent string.
•  This does affect device detection as most of that is done by detecting the user agent.
Clients sending emails based on device, time or location information, will most likely be impacted by this change when sending to Gmail recipients.  The team at Listrak is aware of the change and is actively testing the impact and looking at all options on our end.  Right now there does not seem to be any way to bypass the image caching.