Why iframes are not supported in emails
Get reliable results with basic HTML in your templates
Here's my thesis: you should avoid iframes in your email templates and use pure HTML instead.
Let me explain why.
Before I jump into the arguments, a quick iframe primer. Basically, an iframe is a piece of HTML code that displays one web page on another webpage. That is, for instance, how many people embed a YouTube video on a webpage. Many folks use iframes to display other kinds of content, like social media posts, Google maps, and ads.