Uniquely identifies an attachment.
<AttachmentID> <extension base="uid"> <attribute name="itemReference" type="boolean"/>
Specifies the unique identifier for the attachment.
Specifies that the attachment is an embedded item (for example, mail, appointment, task, note, etc.). If the item is an itemReference, call getItemRequest to retrieve the item. If the item is an attachment, call getAttachmentRequest to retrieve the item.