Can't access email with digital signature in outlook addin?

Question

I'm developing a outlook addin, which access metadata of an email. But i have the problem, that the addin is not shown in the outlook web app, when i select an email with an digital signature. When I select the same email in the outlook rich client then iget the error, that the operation cannot be performed, because the permissions for the message are restricted. I set up the permission in the addin manifest to "ReadWriteMailbox".

Can someone help me, how i can access an email with digital signature in the outlook addin?

Answer 1

Outlook Add-ins overview listed Mailbox items available to add-ins. The following is the quote from the document:

Outlook does not activate add-ins if the current message item, in a compose or read form, is one of the following: Protected by Information Rights Management (IRM), in S/MIME format or encrypted in other ways for protection. A digitally signed message is an example since digital signing relies on one of these mechanisms.

To answer on your question ... you cannot access e-mail with digital signature from Outlook Office.js add-in.

EDIT:

Per Microsoft team comment, digitally sign messages are available to add-ons. I have verified with signed SMIME message, add-ons are active and functionality is fine. Waiting for documentation update.