The vast majority of Email clients typically do not support the latest interactive web technologies. Here is a list of the most common asked-about elements that are either not supported or have limited support by most email clients:
Iframes are used embed external content within a document. Most email clients do not support the iframe tag.
Forms are one of the most common interactive elements on the web, but email clients generally do not support submitting a form on an email.
Background images are not supported by all email clients.
<style> background-image: url("background.png"); </style>
Video: Embedded video is not supported by email clients.