A responsive ad will automatically adjust its size to fit available ad zones. Responsive ads lets you deliver a better reader experience based on a users specific device and screen size.
Standard zone tags generated in Indie Ads Manager will be fixed size, meaning the ads will not adjust their size to fit available spaces.
To make an ad zone responsive, you must 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.
Original Zone Tag
<!-- Newsletter: Presenting (Ad Spot) [email] -->
<a href="https://servedby.indiegraf.com/go2/;ID=185279;size=550x725;setID=626138;uid=%SUBSCRIBERID%%MESSAGEID%;click=CLICK_MACRO_PLACEHOLDER" target="_blank"><img src="https://servedby.indiegraf.com/e061c2b60/img-api/O0lEPTE4NTI3OTtzaXplPTU1MHg3MjU7c2V0SUQ9NjI2MTM4O3R5cGU9aW1n/?uid=%SUBSCRIBERID%%MESSAGEID%" width="550" height="725"></a>
Edited Zone Tag
<!-- Newsletter: Presenting (Ad Spot) [email] -->
<a href="https://servedby.indiegraf.com/go2/;ID=185279;size=550x725;setID=626138;uid=%SUBSCRIBERID%%MESSAGEID%;click=CLICK_MACRO_PLACEHOLDER" target="_blank"><img src="https://servedby.indiegraf.com/e061c2b60/img-api/O0lEPTE4NTI3OTtzaXplPTU1MHg3MjU7c2V0SUQ9NjI2MTM4O3R5cGU9aW1n/?uid=%SUBSCRIBERID%%MESSAGEID%" style="max-width:100%;height:auto;"></a>