Office 365 offers a comprehensive compliance toolset that spans Exchange email, SharePoint and OneDrive for Business documents, and Skype conversations. Some customers store valuable information in Exchange public folders, and have requested that we broaden Office 365’s compliance solution to cover public folder data as well. Previously, external archiving solutions were required to meet this need.
Read more at source: https://blogs.office.com/2015/07/02/announcing-compliance-toolset-for-public-folders/