This worked for me:
src="{0}" width=30 height=30 style="border:0;"
Nothing else has worked so far.
The px needs to be left off, for some odd reason.
This works for me in Outlook:
<img src="image.jpg" width="120" style="display:block;width:100%" />
I hope it works for you.
Can confirm that leaving px out from width and height did the trick for Outlook
<img src="image.png" style="height: 55px;width:139px;border:0;" height="55" width="139">
<img id="_x0000_i1026" src="images/img.jpg" width="120" height="150" />
This worked for me both in gmail and outlook.
make the image the exact size needed in the email. Windows MSO has a hard time resizing images in different scenarios.
in the case of using a 1px by 1px transparent png or gif as a spacer, defining the dimensions via width, height, or style attributes will work as expected in the majority of clients, but not windows MSO (of course).
example use case - you are using a background image and need to position a with a link inside over some part of the background image. Using a 1px by 1px spacer gif/png will only expand so wide (about 30px). You need size the spacer to the exact dimensions.