Microsoft is working on improving the Office 365 Message Encryption (OME) service to reduce the likelihood that emails with one-time passcodes (OTPs) required to read encrypted messages are marked as spam by mail servers. Microsoft is planning to roll out these new Office 365 capabilities and make them generally available to standard multi-tenants later this month. The OME online service is built on Microsoft Azure Rights Management (Azure RMS) and it enables Office 365 customers to send and receive encrypted emails via Outlook.com, Yahoo! Gmail, as well as other email services that come with encryption, identity, and authorization policies.
Source: https://www.bleepingcomputer.com/news/microsoft/office-365-to-make-one-time-passcode-emails-look-less-spammy/