AMP is being adopted by Gmail, Outlook, Mail.ru and Yahoo! as a valid MIME content-type message part. The Python email module could support this, I believe in an RFC-compliant way within the mimetypes module at mimetypes.types_map (and elsewhere as needed, possibly in the parser and generator though I suspect not as it's really utf-8 html other than the kinda silly lightning bolt emoji, which is optional to the AMP spec). My current concern is that the types map dictionary is keyed on filename extensions but AMP MIME (text/x-amp-html) is also .html. We can't have two keys for this and AMP doesn't have its own filename extension.