Unable to open encrypted email in Outlook web

I can encrypt a message and send/receive using Outlook client and read it just fine.  I can read the message with Outlook on my mobile device.  I cannot however view the message using Outlook in O365 web.  I see that the message is an attachment that I can only download but cannot view in the web viewer.  I'm prompted to download and install a trial of Outlook client.  In all the docs I've read, they indicate that viewing in the Outlook web interface should work just fine.  Am I missing a setting to enable this for my org?