Licenses and Limitations of Encryption and Exchange Online in you Microsoft 365 subscription.
Example Send a New message and there is an “Encrypt” button. Great feature but is there a gotcha you need to configure or another license version you require?
Slightly frustrating a button exists even if its not configured and gives your end users and error message.
“Your machine isn’t set up for Information Rights Management (IRM). To set up IRM, sign in to Office, open and existing IRM protected message or document, or contact your help desk.”
You created and new message in Outlook, clicked options, Encrypt, and Connect to Rights Management Servers and get templates
You received this message because RMS isn’t setup in your Microsoft 365 tenancy. Azure Information Protection is only included with certain licenses in Office 365. See License Data Sheet.
OME stands for Office 365 Message Encryption (OME).
Microsoft provide this guide to choosing your activation method.