Using Classic Outlook on Windows for personal email, calendar, and contact management
Hi, Dr. Andler
Thanks for posting in our community.
According to your description, the issue of your concern that one-time pass code not working correctly for the encrypted email.
First, could you please tell us whether you're using O365 for business subscription or not?
Supposed you're using O365 for business account, please be kindly to have a check on your OWA - Outlook Web App to see if there's a same issue or not.
If the issue only happened on your desktop client, please give an attempt for Create an Outlook profile and see if it make any differences.
In addition, please update your Outlook desktop client into the latest version and share it with us for further help.
Hope it works, and please feel free to contact us if there's an update.
Kind Regards,
Zed