Help - Office 365 Backup Policy

Don't use preservation policies as they a SharePoint-only option (still existing, still active, but the wrong choice). The long-term solution for retention of information inside Office 365 is in the new data governance framework where you can create retention policies that apply across more than just SharePoint and classification labels that dictate precisely what happens to information when a retention period expires. See https://www.petri.com/office-365-data-governance for more.