How can I find all encrypted and/or signed emails in outlook?

How can I find those emails and is it possible to make a search folder containing those emails?

I tried several fields and tried to make a search folder, but found no attribute for this search.

The criteria for a custom search folder would be (Search Folder Criteria | "Advanced" tab | "Field" button | All Mail Fields):

Message Class contains IPM.Note.SMIME (for both signed/encrypted messages);
Message Class is (exactly) IPM.Note.SMIME (for encrypted messages only);
Message Class is (exactly) IPM.Note.SMIME.MultipartSigned (for signed messages only that are not encrypted).

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