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.

Symbian platform implementation of IMAP4

The Messaging Application module has implemented all the functionality of standard IMAP4 and conforms to RFC3501.

IMAP4 example

For more details on implementing the IMAP4 MTM functions, see example code.

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