Microsoft Exchange Schema Attributes
In addition to the existing Microsoft Exchange account schema attributes, the following new attributes are added in the schema for new applications. For existing Active Directory applications, the following schema attributes must be added manually if required:

Type of the Microsoft Exchange recipient object. Value 2
indicates that the mailbox type is a Linked Mailbox.

The distinguished name of the Linked Mailbox Shadow Account.

The objectGuid of the Linked Mailbox Shadow Account.