2.2.1.28 PidTagMimeSkeleton Property
Type: PtypBinary ([MS-OXCDATA] section 2.11.1)
The PidTagMimeSkeleton property ([MS-OXPROPS] section 2.804) contains all the top level MIME message headers, all MIME message body part headers, and body part content that is not already converted to Message object properties, including attachments.
The use of the PidTagMimeSkeleton property for converting between MIME messages and Message object format is specified in [MS-OXCMAIL] section 2.4.3.1.