Mimi,
If someone has sent you a photo, in the body or as an attachment, even the attached file can be opened (viewed); downloading doesn't come into the picture ('cuse the pun). The image can either be opened (viewed) or saved. Certainly one may have to get past the allow or permissions bit but, after that...
In Outlook, for example, goes a step beyond, in that one can Preview a file, say a PPS & not, even, actually Open it, per se.
Drew