You must also provide a proxy generation DLL to be used with your gateway. The proxy generation DLL does the work of mapping between Microsoft Exchange Server addresses and addresses in the foreign system’s address format.
On outgoing messages, the sender’s address and any other Microsoft Exchange Server recipients’ addresses are converted to the foreign system’s address format so that the recipient on the foreign system will be able to reply to those people.
On incoming messages, the proxy generation DLL maps the Microsoft Exchange Server recipient’s address from the foreign system format to Microsoft Exchange Server format so that the server can actually deliver the message to the proper Microsoft Exchange Server mailbox. Additionally, addresses are converted for any other recipients listed in the message that also have mailboxes on the server.