30. The method as recited in claim 1 , wherein the primary type indicates the behavior of a message attachment attached to the single message item, wherein the message attachment includes: an electronic message relationship field representing a link to the single message item, the link indicating that the message attachment is associated with the single message item; a type field representing a message type of the electronic message linked to by the link represented in the electronic message link field, the message type implying a behavior of the electronic message; an IsPinned field representing the deletion status of the message attachment with respect to the electronic message; an IsTrusted field representing trust information related to the message attachment; and an attachment state field representing the type and behavior of the message attachment.
30. The method as recited in claim 1 , wherein the primary type indicates the behavior of a message attachment attached to the single message item, wherein the message attachment includes: an electronic message relationship field representing a link to the single message item, the link indicating that the message attachment is associated with the single message item; a type field representing a message type of the electronic message linked to by the link represented in the electronic message link field, the message type implying a behavior of the electronic message; an IsPinned field representing the deletion status of the message attachment with respect to the electronic message; an IsTrusted field representing trust information related to the message attachment; and an attachment state field representing the type and behavior of the message attachment. 31. The method as recited in claim 30 , wherein the message attachment further includes: an attachment source relationship field representing a link to a database item where the message attachment was accessed.