If a user sends an email with Email RMS (e.g. DO NOT FORWARD, or COMPANY CONFIDENTIAL) to an outside external user that is also using Exchange Online and Outlook, what is the expected experience?
We are testing it out and that user gets the email, but is has a red dash icon on it, and if they try to open it it says they need to request more information from the sender, but they are never able to actually open it.
If we send it to external users in gmail and yahoo and other services like that, it works fine, they have a link to click to open and view the protected email in a browser.
When you use the Company Confidential template then it prevents outside people from being able to open the email, so it sounds based on the behavior you are reporting that it is working as designed by not allowing that recipient to open up your internal company confidential communications.
However, you should be able to send a "Do Not Forward" email to an external recipient and they should be able to open it if they open it in Outlook or OWA, especially if they are an existing O365 user.
Feel free to send me a test and I can let you know if I receive it or not, my email is joe at patriotconsultingtech.com