Microsoft is working on expanding the capability to revoke encrypted email messages sent using the Office 365 Message Encryption (OME) service to regular users.OME is built on Microsoft Azure Rights Management (Azure RMS) and it combines rights management with email encryption capabilities. Microsoft doesn’t explain what will happen with the revoked encrypted messages, according to its support site, when admins revoke such emails, the recipients receive ‘The message has been revoked by the sender’ errors on trying to access the encrypted emails. The company is also in the process of adding improved external email forwarding controls which will allow Office 365 admins to enable the feature only to select employees in their organizations.
Source: https://www.bleepingcomputer.com/news/microsoft/office-365-to-let-regular-users-revoke-encrypted-messages/