Gmail recently started caching one copy of an image in email messages and serving it to multiple Gmail users. This only affects Gmail users who use Gmail’s web interface or Gmail apps – IMAP users are not affected. Here’s what will and won’t change for iMM users as a results of this new Gmail behavior.
The iMM’s response counts for unique views won’t be affected, since each email recipient gets their own unique image source URL. Gmail may cache that image if it likes, but it won’t prevent the image from being loaded at least once for each recipient.
Since the image will be loaded through Gmail’s cache-fetch system, the IP address and email platform of some Gmail recipients will appear to be Google’s data centers, rather than their actual location and platform.
Multiple (nonunique) view reports may be affected, such as the “Raw HTML View report.” This kind report has been subject to email client caching since HTML email was invented, so there’ll be no new behavior resulting from this Gmail change. Most iMM reports are based on the unique view count, so this will have little effect on iMM users.
Click tracking won’t be affected at all. Location, IP address, platform, and number of interactions will all continue to be tracked and reported accurately.