Hi @L. Smeets ,
Welcome!
When I'm sending an new 'normal' e-mail it's signed and working properly.
So, here, may I understand that you could successfully create a new email message, encrypt it and send it out but will get troubles when using "concepts"?
If yes, what does the "concepts" you mentioned here mean?
By the way, currently in Microsoft Q&A we only support English, so could you please provide us with English error screenshot so that we can conduct more researches about your issue?
Any update, please feel free to post back.
If an Answer is helpful, please click "Accept Answer" and upvote it.
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.