The Microsoft Connector for POP3 Mailboxes no longer supports Authenticated POP or CRAM-MD5 encryption
Windows Small Business Server 2003 Setup will upgrade the Microsoft Connector for POP3 Mailboxes. Because the connector no longer supports Authenticated POP or CRAM-MD5 encryption the authentication type for one or more POP3 mailboxes will be changed to basic authentication. However, the connector does support Secure Password Authentication (SPA).
To continue Setup, select the I acknowledge all warnings check box.