There was an announcement for a new feature of E5 being called Advanced Data Governance. It was buried in an announcement back in Sept 2016.
Some time ago, Office 365 made several announcements for being able to consume corporate data from other major platforms. There is a new Advanced Data Governance feature that will be coming to Office 365 that will provide you a dashboard that will give insight to the type of data you have, how it is classified, and how it is going to be retained. There will also be tools to assist you with the data import process to filter out data that you do not need to retain, and you will have a tool that will allow you to set a central retention policy across all Office 365 solutions. This is super exciting and I highly recommend you watch the session on this at the Ignite Conference.
Announcement - https://blogs.office.com/2016/09/26/applying-intelligence-to-security-and-compliance-in-office-365/
Ignite Conference Video - https://myignite.microsoft.com/videos/1323