Enable the encrypt button in Outlook for Business Premium subscriptions
Enable the OME encrypt button in Outlook for users with a Business Premium with OME bolted on. This appears in OWA so why shouldn't it also be available in Outlook. If you are paying for the licence you should get the tools you need to use it.
C Ayosa commented
If I may also add that Office Home and Business be included in it. As per reference: https://support.office.com/en-us/article/outlook-license-requirements-for-exchange-features-46b6b7c5-c3ca-43e5-8424-1e2807917c99, RMS Template is not available on the said build.