IMAP4 +Concepts

This section describes the Internet Message Access Protocol (IMAP4) and +its implementation on the Symbian platform.

IMAP4 protocol

IMAP4 +is one of the most common Internet standard protocols for retrieving emails. +It is an application layer Internet protocol operating on port 143 that allows +a local client to access email on a remote server.

The current version, +IMAP version 4 revision 1 (IMAP4rev1), is defined by RFC 3501. Eariler, IMAP4 +was called Internet Mail Access Protocol, Interactive Mail Access Protocol +(RFC 1064), and Interim Mail Access Protocol.

The default port for +IMAP4 to download messages is 143, but if a client establishes a secure connection +(over SSL or TLS) for IMAP4 to download message, the port is 993.

Most +email clients support either POP3 or IMAP to retrieve messages; however, few +Internet Service Providers (ISPs) support IMAP. IMAP4 supports access to the +mail store in both modes of operation—connected (online) and disconnected +(offline).

Emails are generally sent to an email server that stores +received messages in the recipient's email mailbox. The user later retrieves +these messages with either a web browser or an email client that uses one +of a number of email retrieval protocols.

Email clients using IMAP4 +generally stores messages on the server until the user explicitly deletes +them. This allows multiple clients to access the same mailbox. However, the +client may store local copies of the messages, but these are considered to +be a temporary cache; the server's store is authoritative.