Postfix will receive e-mail and deliver it to the user's inbox, but additional software is required to allow users to read their e-mail with ease. There are two standards for retrieval of e-mail from a host. The first is called Post Office Protocol (POP). POP3 is the most commonly used version of POP. This is normally used to download e-mail from the server, store it in a client application, and remove the e-mail from the server. This is often used by Internet Service Providers. The e-mail is subsequently manipulated by the client application, for example, Windows Live Mail or Mozilla Thunderbird.
The second protocol is called Internet Message Access Protocol (IMAP).The IMAP system is usually used when you want a copy of each e-mail to stay on the server. IMAP allows users to create folders for e-mail and to move or copy e-mail between the folders. The client application accesses the e-mail on the server, but does not have to store it on the client machine...