What to choose for a corporate event feed?

Question

Active Directory

I would like something similar to Twitter, a kind of intraportal, with domain (transparent) authorization. So that any employee (or not any) could go to the page and post the news, his full name and timestap would be automatically added to the news. In principle, this is already enough, ideally, sending to email (with settings) and tags \ hashtags at the request of the user. What do you advise?