2.3.3.7 attAttachData Attribute Handling by the TNEF Reader

If the PidTagAttachMethod property ([MS-OXCMSG] section 2.2.2.9) of the original attachment contains the value 0x0005 (ATTACH_EMBEDDED_MSG) or the value 0x0006 (ATTACH_OLE), then the TNEF Reader SHOULD ignore the attAttachData attribute, as specified in section 2.1.3.3.11.