Microsoft have announced that they’re removing Message Delivery Reports from Exchange Online. The removal will start on 15th May and be completed by the middle of June 2018.
Delivery Reports have already been removed from Exchange Online Admin Centre and Outlook on the Web however the feature is still available in Outlook.
Currently when users use the Delivery Report in Outlook they are redirected to a web page which shows the delivery status of the message however after the change a warning will be displayed showing: “Sorry, the Delivery Reports feature is no longer available in Office 365.”
Once removed it will be down to Exchange Online Administrators to run a message trace to check the delivery status of a message:
Microsoft have published this under MC133711 for more information.