Microsoft has added Yammer Enterprise to all Office 365 Midsize Business and Education plans, the company said in a blog post.

All existing Office 365 Midsize Business and Education customers will receive licenses for Yammer Enterprise. Additionally, customers who would like to have their own clients or external workers on the platform will no longer have to purchase additional Enterprise licenses.

Microsoft says the update will help to reduce "the friction in cross-organization collaboration" and "enable...users to work with customers, partners, and parents and students without having to worry about additional costs."

What is Yammer?

Yammer offers businesses a private social networking platform. With an interface similar to Facebook's, the system, which is used by more than 200,000 companies, allows workers to privately collaborate, share content and communicate with one another.

Microsoft made Yammer available to all Enterprise customers in November. In 2012, Microsoft purchased Yammer for $1.2 billion, roughly four years after David Sacks, a former PayPal executive, launched the social networking company.