If you don't remember, AMP for Email provides the ability to utilize dynamic content functionality in the email inbox. Bounteous explains: "With AMP, functionality previously relegated to landing pages (such as booking an appointment or even making a purchase) became possible within an email itself."
Verizon/AOL/Yahoo: On October 14th, Verizon announced that AMP for Email support has launched in Verizon's Yahoo Mail platform. They clarify that it works only in the Yahoo Mail webmail interface, and not in AOL Mail or the Yahoo Mail mobile app.
Google/Gmail: Google launched Gmail support for AMP for Email back in March, 2019. Google notes that in addition to webmail support, AMP for Email is supported in the Android and iOS Gmail app, as well. (Note that AMP for Email content is NOT going to display for Gmail users who use iOS's default email client. It does not offer AMP for Email support.)
Microsoft/Outlook.com/Hotmail: Microsoft was at one time going to provide AMP for Email support for Outlook.com, but they announced in September that they were winding down testing and that there were not going to proceed.