2.2.2.1.1 PidTagMessageClass Property

Type: PtypString ([MS-OXCDATA] section 2.11.1)

The PidTagMessageClass property ([MS-OXCMSG] section 2.2.1.3) specifies the type of the Message object. The value MUST be "IPM.Task" or begin with "IPM.Task.". The string is case-insensitive.