2.1.3.3.18 attDelegate Attribute
The attDelegate attribute MAY<2> be supported.
The attDelegate attribute is a message-level attribute that is a meeting attribute that maps to and from PidTagReceivedRepresentingEntryId property ([MS-OXOMSG] section 2.2.1.25).
The content can be transported as a binary large object (BLOB).
For details about how the TNEF Writer handles this attribute, see section 2.2.3.13. For details about how the TNEF Reader handles this attribute, see section 2.3.3.12.