Hi @ Jennifer ,
In my tests, I got the same result when I sent an encrypted email to a shared mailbox.
I can receive a redirect link in the Outlook client, but I can't view the message content. After clicking the link, I will be redirected to OWA to view the content of the email.
However, encrypted messages sent to the user mailbox can be viewed directly in the Outlook client.
Therefore, as a workaround, I recommend that you use the Open another mailbox option to open the shared mailbox in OWA to view messages.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.