POP3 Routing

When POP3 is used to retrieve messages from a user's Microsoft Exchange Server Inbox, the client submits requests to the server. POP3 e-mail clients can retrieve messages only from their Microsoft Exchange Server Inbox. They do not have access to private or public folders or to encrypted messages. When a POP3 client sends a message, the Internet Mail Service routes messages to the Microsoft Exchange Server computer or to other SMTP hosts, depending on the recipient's address.