Outlook on the Web (OWA) 2016 in Office 365 - Recover Deleted Items
This article explains how to recover deleted items using the Outlook on the Web (OWA) in Office 365.
Restoring Items in Outlook on the Web
You can recover a deleted folder with all of its messages from OWA as long it is still in your Deleted Items folder. Unfortunately, you cannot recover a folder that has been permanently deleted.
See the following Microsoft Support articles for more information.