This article explains how to stop iOS Mail from downloading remote images, a feature that is enabled by default in the Mail app. This information applies to devices running iOS 12, iOS 11, or iOS 10.
How to Prevent Emails from Loading External Images in Mail for iPhone and iPad
When your iPhone, iPad, or iPod touch loads external images into the Mail app, it uses your data allotment and battery power. It can also alert spam senders that you've opened their messages.
You can disable remote images on an iPhone or other iOS device through the Settings app. Here's how.
Open the Settings app.
