I read this thread: Is JavaScript supported in an email message?
But still the question remain relevant to me.
So how does really Yammer messages are actionable in Outlook?
There are thumbs up that's possible, there're sometimes voting that's possible. And from my memory (rather bad on this one) I think Gmail too allow that to a certain extent.
Are there any libraries that can be embedded in the Email HTML construction that support this kind of feature?
-- Edit
An example screenshot is as follows. Sorry about the black boxes as I had to remove all private info from there). As you can see the Thumbs up is a link works indeed, without having to visit Yammer. All inside Outlook. (Note the Red arrows marked are there for the "Like" functionality and the "Others voted" functionality)
The state change that I invoked is notable in the Email message as well as Yammer post in the same exact way.