I followed the recommendations: 

• Your logo should be at least 200 pixels wide and 200 pixels tall.
• The maximum size of the printed logo is 400 pixels wide and 200 pixels tall.

But it still doesn't work.

I even went so far as to make the logo 100 pixels wide and it still wont work; shows up enlarged and cut in half... ???

Make your log square. Like 250x250 and it should work

I tried that, but it is not working. Showing a broken link in Outlook 365. I see this has been an ongoing problem. Any resolutions that anyone knows of yet?

Hey @JC160, thanks for checking in on this issue. I went to look for updates related to the display problems on Outlook though there isn't anything that I can access and share out right now. We'll certainly announce any developments that come through—sorry for any confusion this may cause for your customers.