POP3 and IMAP4

By default, POP3 and IMAP4 are disabled in Microsoft Exchange Server 2010. To support clients that still rely on these protocols, you must first start the POP3 and IMAP4 services on the Exchange 2010 Client Access server. You must also configure SMTP for your POP3 and IMAP4 clients to send e-mail

Differences Between POP3 and IMAP4

POP3 is a frequently used e-mail Internet protocol. By default, when POP3 e-mail applications download e-mail messages to a client computer, the downloaded messages are removed from the server. When a copy of your user's e-mail isn't kept on the e-mail server, the user can't access the same e-mail messages from multiple computers. However, some POP3 e-mail applications can be configured to keep copies of the messages on the server so that the same e-mail messages can be accessed from another computer. POP3 client applications can only be used to download messages from the e-mail server to a single folder (usually the Inbox) on the client computer. The POP3 protocol can't synchronize multiple folders on the e-mail server with multiple folders on the client computer. POP3 also doesn't support public folder access

E-mail client applications that use IMAP4 are more flexible and generally offer more features than e-mail client applications that use POP3. By default, when IMAP4 e-mail applications download e-mail messages to a client computer, a copy of downloaded messages remains on the e-mail server. Because a copy of the user’s e-mail message is kept on the e-mail server, the user can access the same e-mail message from multiple computers. With IMAP4 e-mail, the user can access and create multiple e-mail folders on the e-mail server. Users can then access any of their messages on the server from computers in multiple locations