Gmail drops "display images" option for iOS and Android; new policy to start next year3
Once this policy starts, iOS, Android, and even desktop users of Gmail will see images appear on their received messages without having to okay them first. And at the same time, the images are being checked for all known viruses and malware by Google. But if you are basically cynical about Google's ability to block malware, or you believe that people are inherently evil, or you think that someone is after you, you can go into the Gmail settings and select "Ask before displaying external content," and you will be asked once again to approve all images before they are shown.
The new policy on images is starting today for desktop PCs and will begin rolling out to iOS and Android mobile apps early next year.
source: Google, GoogleSupport via AndroidCentral