Yammer is a private social network that helps you get connected to the right people, share information across teams, and organize around projects. Only your coworkers can join, so your communications on Yammer are secure and visible only to people within your organization.
Yammer is a Microsoft company, though it’s not completely integrated into Office 365 yet. When you launch Yammer from within Office 365, you’ll be redirected to yammer.com. Sign in with your Yammer username and password, or create an account using your corporate email address.