implementation of the Internet Information Server installation. Outgoing messaging also remains the same, because the code is fully compatible and it has the same functionality.
In a server that’s being upgraded from Internet Information Server 4.0 to Exchange 5.5, incoming mail is routed into a secure Exchange mailbox. As a result, administrators or developers must create mailboxes for each inbound mail address and assign Windows NT service-account permissions to those mailboxes. In addition, developers of server-based applications need to ensure that the server has the proper Windows NT permissions to open a mailbox.
Microsoft Exchange Introduction to Collaboration Data Objects White Paper11