Office 365 Message Encryption

Question

When we receive Office 365 encrypted messages to our company email we cannot open them (email isn't Outlook). Below is the describes the process we take to open these messages (Steps 1-6) along with attachments. Also, the email contains an attachment "rpmsg" which we also cannot open. I found that Outlook should open these types of files. However, I cannot open them when using "Open with" then Outlook. Any help you can lend would be much appreciated.

1. We click on Read the message (see pic 001)
2. A box appears Sign in with a One-time passcode and we click on it (see pic 002)
3. A box appears We sent a one-time passcode to the company email address (see pic 003)
4. Email is received with one-time passcode (see pic 004)
5. We enter the One-time passcode in the empty box (see pic 003)
6. We receive a message You don't have permission to view this message (see pic 005)

Answer 1

The passcode that we receive shows below info:

Web Email: ******@messaging.microsoft.com

Web Name: Microsoft Office 365 Message Encryption

ALSO...

I copied/pasted the original message we received from our client:

--------------- Original Message ---------------
From: **removed for privacy**
Sent: 6/3/2022 5:55 PM
To: m**removed for privacy**
Cc: **removed for privacy**
Subject: FW: Transportation Learning Center ****

Chris ***removed for privacy** has sent you a protected message. <br> <br> <br><br> <br>Read the message<br> <br> <br>Learn about messages protected by Office 365 Message Encryption.