POP3

Local email clients use the Post Office Protocol version 3 (POP3), an application-layer Internet standard protocol, to retrieve email from a remote server over a TCP/IP connection. Email clients using POP3 generally connect, retrieve all messages, store them on the user's PC as new messages, delete them from the server, and then disconnect. In contrast, the newer, more capable Internet Message Access Protocol (IMAP) supports both connected (online) and disconnected (offline) modes of operation.