2.2.5.12 PidNameXCallId
Type: PtypString ([MS-OXCDATA] section 2.11.1)
The PidNameXCallId property ([MS-OXPROPS] section 2.483) is a unique identifier associated with the phone call.
The relationship between this property and the MIME header is specified in [MS-OXCMAIL] section 2.1.3.2.3 and [MS-OXCMAIL] section 2.2.3.2.23.