Microsoft Exchange directories let you create special objects called External Recipients. These can be thought of as address book entries that represent recipients in external messaging systems. You can modify the Schema Mapping policy to map an eDirectory User object to a remote object instead of the Mailbox object. You should now be able to map this to any object. For example:
<class-name>
<nds-name>User</nds-name>
<app-name>remote</app-name>
</class-name>
If you decide to make this change, you should also add the Internet EMail Address attribute as a required attribute to the Create policy as shown in the following example:
<create-rules>
<create-rule class-name="User">
<required-attr attr-name="Given Name"/>
</create-rule>
</create-rules>
An Internet EMail Address attribute is required to create an External Recipient object in the Exchange directory. Failure to add the Internet EMail Address attribute will result in an error when trying to create an External Recipient.