Dynamic Emails with Gmail
Google introduced a new to Gmail feature called "Dynamic Emails" - a way for businesses to email you can include live changes and enable you to interact with the emails.
When you receive a dynamic email, a lightning bolt icon will show up next to the date the email was sent.
According to Google's blog, they've implemented "best-in-class" privacy and security features. After inspecting the page, it looks like, at least for an email about Google Docs comments, the Gmail page makes a request to a specified URL, and the URL returns any changes. The feature implements an
amp-list, which is part of Google's AMP project.
As an added security measure, Google has to review a business before letting them send a dynamic email.
If you're interested in creating dynamic emails, you can view this documentation page or read more about AMP Emails in this article
If you'd like to learn more about Dynamic emails, check out this blog post on Google's blog.