You can configure Exchange 2007 Client Access servers to connect to mailboxes located on Exchange 2003 servers. However, when you do this, you must disable Secure Sockets Layer (SSL) encryption and enable Basic authentication on the Exchange 2003 server. Because the user name and password are sent in clear text when Basic authentication is used without encryption, we recommended that you secure the traffic between the Client Access server and Exchange Server 2003 server by using Internet Protocol security (IPsec).

To perform the following procedures on a computer that has the IMAP4 service enabled, the account you use must be delegated the Exchange Server Administrator role and membership in the local Administrators group for the target server.

For more information about permissions, delegating roles, and the rights that are required to administer Exchange Server 2007, see Permission Considerations.

 To use the Exchange Management Shell to configure IMAP4 access to Exchange 2003 servers

1. To configure IMAP4 access to Exchange 2003 servers by using the default port value, run the following command:

   Set-ImapSettings -ProxyTargetPort 143

2. To disable IMAP4 access to Exchange 2003 servers, run the following command:

   Set-ImapSettings -ProxyTargetPort 0

For more information about syntax and parameters, see Set-IMAPSettings.

For more information about how to use IMAP4 with Exchange 2007, see the following topics:

• Overview of POP3 and IMAP4
  
• Managing POP3 and IMAP4