We have configured OME for our company recently, but we are running into an issue when recipients attempt to open the message in one scenario.
When we send an encrypted message from the Web portal, via the "Encrypt" button or via a mail flow rule to "Encrypt any message where the body contains the word...", we have no issue, and the recipient can click on the Encryption link and log into the portal.
However, When we send the message from an Outlook client the following error occurs for the recipient. The user clicks on the "read the message" link and is directed to the Outlook.office365.com/encryption portal as expected. When they click on the "Sign in with a work or school account" and Successfully sign in with a Microsoft account, it loops them right back to the same "Sign in to view your message, Sign in with a work or school account" screen.
We have attempted with multiple Microsoft account, both business and personal to no avail. Also of note, the "One-time passcode" option works without issue.
If the issue is with only one recipient this could be a browser cache issue on their end wherein the recipient could already be logged in to a different account, ask them to open the email on a different browser or incognito window and then check.
If the issue is with multiple recipient ask the sender to configure a fresh account on Outlook and check.