2.1.3.3 Special Considerations for S/MIME Secure Messages

The best body algorithm, as specified in section 2.1.3.1, yields an accurate result for a clear-signed S/MIME (Secure/Multipurpose Internet Mail Extensions) message, meaning the value of the PidTagMessageClass property ([MS-OXCMSG] section 2.2.1.3) is "IPM.Note.SMIME.MultipartSigned". However, the result of the best body algorithm is undefined for other types of S/MIME messages, for example, when the value of the PidTagMessageClass property is "IPM.Note.SMIME". For details about these message types, see [MS-OXOSMIME].