The POP (Post Office Protocol) and IMAP (Internet Mail Access Protocol) protocols allow a client application to directly access mail located on a remote server. But, as is often the case with communication software (but this is changing), most POP/IMAP application communicate with the server using cleartext by default.
To get encrypted communication, action is required on the part of the user.
This section will describe two methods one may use their POP/IMAP capable mail client to securely access mail on their POP/IMAP UNIX/linux server.
Both methods apply to systems located within NRC, as well as systems people are using to connect to NRC from home.
First, it should be noted that POP and IMAP are two different protocols. POP uses port 110 whereas IMAP uses 143. A port is an access door one uses to communicate to different applications on UNIX/linux. POP uses port 110. IMAP uses port 143. sendmail, the application that accepts mail on the servers, uses port 25. SSH uses port 22. The web uses port 80.
All systems use the same port for the same applications, and all application servers listen to the same ports. This allows for different applications using the same protocol (ex: pine, evolution, netscape, Eudora all use the POP protocol) to know how to contact remote servers because they know which port, and which protocol, to communicate with.