I was just about to tell a client we couldn't use 24-bit PNGs when I ran this test and they actually look okay... ?
Can anyone verify do PNGs with alpha transparency work in Outlook 2007 and less? Or are the test machines using a newer IE that fixes it, and is that a realistic expectation if the machine has Outlook 2007 or older on it.. ?

Test results -
https://litmus.com/checklist/emails/public/3de02a4