How do I read client's responses to my encrypted emails?

Hi Gyan, you have my experience down to the T! I appreciate the explanation of its process during sending and receiving back the email. Very concise!

Yes I also receive those message_V2.rpmsg attachments. However I can't double-click on them (in Outlook desktop) to read those messages. Windows asked me which program the file type needs to be associated with. If I were to manually browse to the Outlook program, Windows just throws an error along the lines of the file type can't be associated with the program. I am trying my best to troubleshoot this on my own, but I am at roadblock again with this particular issue. 

I'm seeing references from videos and articles that I supposedly can open this file on OWA, but clicking on it just downloads the rpmsg file to my local computer. Have you had experience on what the issue is and what I can do to fix this? Apologies if this is a duplicate reply. This website seems to want to approve of my reply before posting.