POP-3 stands for the post office protocol, revision 3. It is the most common way for e-mail reader programs (such as Outlook, Pegasus, Eudora or Netscape) to retrieve their e-mail from a server. Since your NetWinder can act as an e-mail server, it provides the POP-3 protocol.
POP-3 is a very simple service and needs no configuration options. If you want to allow e-mail readers to access their mail via POP-3, be certain to enable the POP-3 server on the network services screen.
Newer, more advanced e-mail readers can also use the IMAP protocol to access mail. If you enable POP-3, you may also want to enable the IMAP service.