Use Email Schemas (Microdata and\or JSON-Ld)

[shalecraig]

Schemas in emails can be used to represent various types of entities and actions. Email clients that understand schemas, such as Gmail, can render entities and actions defined in the messages with a consistent user interface. In the case of Gmail, this means that the emails can display quick action buttons that let users take actions directly from their inboxes...

Shamelessly pulled from here