https://www.bleepingcomputer.com/news/microsoft/office-365-to-let-regular-users-revoke-encrypted-messages/

Microsoft is working on expanding the capability to revoke encrypted email messages sent using the Office 365 Message Encryption (OME) service to regular users as part of a larger effort to prevent data leaks and enterprise data theft.

OME is built on Microsoft Azure Rights Management (Azure RMS) and it combines rights management with email encryption capabilities.