If the recipient is local, that is, on the same server as the originator, the Microsoft Exchange Server information store delivers the message directly to the recipient's mailbox. The recipient's distinguished name is used to deliver the message.
As shown in the following illustration, a message from MarcOI is delivered to NelsJ and RoseG by the information store on the same server computer.
A recipient is considered to be local if a distinguished name for the recipient is available in the directory that matches the local site and this distinguished name does not identify a custom recipient. If the recipient has only an O/R address that matches the local site O/R address space, a distinguished name is found by proxy search if the recipient is a valid local recipient.
Address space filtering is performed in the routing routine to ensure that O/R addresses matching the local site O/R address space are not sent out of the site. If a recipient is to be routed through the GWART but matches the local O/R address space, this recipient is marked for an NDR.
To avoid NDRs
If a local recipient originally had a distinguished name and an O/R address is found by a proxy search, the P1 recipient address is not re-encoded because the O/R address is not required when routing locally. The exception to this is when disclosure of recipients is allowed, in which case the O/R address must be included to prevent interoperability problems.