[ramiss]

I also used to find this very frustrating. However, I have since been turned around because of how spammers use images:

Spammers use an image server that will report who has viewed the images. Basically when you download/view images in spam the spammer gets a report that your email address is legit.

Outlook for the PC will allow you to then set trusted senders to automatically view images. It is not fool proof since an address can be spoofed but it is a good compromise.