The fix is adding <font color="#ffffff">text</font> inside.
Credit goes to the folks at Email Monks who published this handy guide in May 2017: https://emailmonks.com/blog/email-coding/email-rendering-issues-in-outlook-and-hacks/
<a style="color:#E3A216; text-decoration:none;">
I found the solution by peaking into the code that Email Monks used for their Holiday Email Marketing. It showed no shrinking images.
You need to replace <html> with
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office">
I kept the doctype as
I'll do some more testing but if all is well, I'll be updating all our base templates. Thanks Email Monks...
Not sure if you've resolved this or not, but is there a reason why you are not specifying the td size and the image size of the background image?
Here's Campaign Monitor's sample code from https://backgrounds.cm/:
<td background="https://i.imgur.com/YJOX1PC.png" bgcolor="#7bceeb" width="120" height="92" valign="top"> <!--[if gte mso 9]> <v:rect xmlns:v="urn:schemas-microsoft-com:vml" fill="true" stroke="false" style="width:120px;height:92px;"> <v:fill type="tile" src="https://i.imgur.com/YJOX1PC.png" color="#7bceeb" /> <v:textbox inset="0,0,0,0"> <![endif]--> <div>