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.

iframes display well on web pages but not in email messages.

That's one reason why most of the big email clients (Gmail, Yahoo, Hotmail) do not support iframes in messages.

Another reason is security. Because iframes pull data from another website, they create a backdoor for malicious code that can lead to all sorts of nasty outcomes, like keystroke tracking, phishing, and heaps more.

A third reason not to use iframes in email templates is usability. Iframes are not mobile responsive, which means email messages with iframe content can deliver a sub-par user experience. If your aim is to make a strong positive impression, why take a chance with a technology that just isn't a good fit for emails?

Except for the big content companies like YouTube, I suggest you avoid iframe embeds and use regular HTML. The results are reliable and positive.

Here's an example.

I'm promoting a coffee shop and want to include a Google map in my email template. At first, I followed Google's embed instructions and created a test email. The result was bleak. None of my test emails displayed the map. Then I remembered that the iframe embed tool works great for web pages but not email templates.

The solution was simple. Take a screenshot of the map, upload the picture to the template, and then attach the Google map URL to the image.

The result was a clean, mobile-responsive message in the test messages. If a reader wants more map detail, they simply click the map image. The live version of the Google map displays.

That's my argument.

iframes don't belong in email templates.