So far, Gmail across all platforms has offered users the feature whereby it blocks the display of images embedded in a message from all but trusted senders. There’s a good reason why that is, as unlike with the text of an email that gets delivered to you through Google’s systems, when you view images in an email, you’re connecting directly to someone else’s server. That not only can be used to verify if you actually read the email, potentially violating your privacy, but reveals your IP, and by extension, your rough location. Google finally thinks it has come up with a way to both keep you safe and save you from having to hit “show pictures” on every email, and it’s rolling the change out to phones soon.
Basically, Google’s going to act as a go-between for these images. It will copy the files onto its servers, scan them for any potential malware (and yes, there have been buffer overflow exploits tied to image files), and serve them up directly to you when you read the mail – that way, all the sender knows is that Google retrieved the images, and gets no extra info about you in the process.
If you’re not comfortable with this, you can always disable it in settings and keep things working the old way. Desktop users will start seeing the changes today, and Google says that Android and iOS will make the switch early next year.