Seriously, check for malware, viruses, and other corruption on your computer. That is a possible cause; else the images themselves are corrupt, your emails bad.
Try the browser version of Outlook or the installed version of Office 365 Outlook. I've been using Microsoft products since they first came out, including especially Outlook. I have never seen problems like you are reporting and if you've done a new, clean setup, that's likely not the problem.
LOL
I tried turning off my internet security, checked for malware, ran a diagnostic on my software. If it was just doing that on Windows 7, or if Thunderbird was doing the same thing, then I'd be worried, but since Thunderbird works fine it's got to be something in Outlook, but I'll be darned if I can figure out what it is.