"Yammer is a private social network that helps employees collaborate across departments, locations and business apps."
"Used by more than 200,000 companies worldwide."
Yammer - Wikipedia, the free encyclopedia
Yammer, Inc. is a freemium enterprise social networking service that was launched in 2008 and sold to Microsoft in 2012.
Yammer is used for private communication within organizations and is an example of enterprise social software. The tool was originally developed as an internal communication system for the genealogy website Geni. Access to a Yammer network is determined by a user's Internet domain so that only individuals with appropriate email addresses may join their respective networks