As announced in November 2021, REST API will be fully decommissioned by Microsoft in November 2022 globally for all customers using Microsoft Exchange Online. 


This means we will be transitioning to Graph API, and we kindly ask all customers using Microsoft Exchange Online (Cloud, MS356) to switch from REST API to Graph API if possible, in order to continue providing the same functionalities of the Phishing Report Button.


From Microsoft | [DEPRECATED] Use the Outlook REST API