I received a mail from Google+ saying that someone I knew recently joined Google+. The email had an interactive red-box which allowed me to add the user to my circles. As far as I am aware, emails do not include running javascript. How is this achieved?Screenshots:The original emailon hoverfinal result
How are Google Plus emails interactive?
email;google plus
This is a specific integration between Gmail and Google+. If you'll look at those messages in a regular email client, you won't see this interactivity. Only if you read them with Gmail web ui, Android or iOS Gmail clients.As for specifics of how it's achieved, I imagine that is Google's 'secret sauce'. :)