Making responsive email images

To make an image responsive, you need to edit the tag slightly at the end replacing the size with style="max-width:100%;height:auto;" which allows the image to reduce in size but not grow beyond the original size.

Example:

Original Tag

<!-- 728x90 email [email] --> <a href="https://servedbyadbutler.com/go2/;ID=XXXXXX;size=728x90;setID=357745;uid=[EUID_HERE];click=CLICK_MACRO_PLACEHOLDER" target="_blank"><img src="https://servedbyadbutler.com/adserve/;ID=XXXXXX;size=728x90;setID=357745;type=img;uid=[EUID_HERE];" width="728" height="90"></a>

Edited Tag

<!-- 728x90 email [email] --> <a href="https://servedbyadbutler.com/go2/;ID=XXXXXX;size=728x90;setID=357745;uid=[EUID_HERE];click=CLICK_MACRO_PLACEHOLDER" target="_blank"><img src="https://servedbyadbutler.com/adserve/;ID=XXXXXX;size=728x90;setID=357745;type=img;uid=[EUID_HERE];" style="max-width:100%;height:auto;"></a>