The Internet Message Access Protocol, commonly known as IMAP, is an application layer Internet protocol that allows a local client to access e-mail on a mail server without dowloading it. In other words, it permits a "client" email program to access remote message stores as if they were local. That's why email stored on an IMAP server can be manipulated from a desktop computer at home, a workstation at the office, and a notebook computer while traveling, without the need to transfer messages or files back and forth between these computers. IMAP's ability to access messages from more than one computer has become extremely important as reliance on electronic messaging and use of multiple computers increase. Think about webmail, for instance, that allows one to read his e-mails in a cybercafé. IMAP is using the TCP port 143. IMAPS (IMAP over SSL) gives a secure access to the server via SSL. It is using the TCP port 993.