Chunk Method to Process Emails

This section describes the chunk method to process email messages.

From Symbian OS v9.4 onwards, POP3 and IMAP email MTMs can use the plain text format for storing email messages (in addition to rich text format). The entire email message is not created in the RAM. Only chunks of the message are stored in the RAM at a time, as writing or reading is done asynchronously. This decreases RAM usage and increases the performance of downloading and storing email messages.

The CMsvStore class is modified with the following APIs to enable chunk method:


A chunk is a substantial amount of an encapsulated email message that is processed in plain text format. The following table provides the default chunk size value that you can have for POP, IMAP, and SMTP.

Protocol Default chunk size


2000 bytes


20480 bytes

You can modify this value using the KImapDefaultFetchSizeBytes parameter.


2000 bytes

The chunk method enables you to limit the need for outbound buffering of an email message in RAM on the client side. It modifies (breaks) the body of a message in order to transfer it as a series of chunks. Each chunk contains a size indicator, followed by a flag that contains entity-header fields, which can be used by the recipient to verify if the email message received is complete or partial.

The method of processing email messages in chunks (plain text format) is provided in addition to processing email messages in rich text format. Licensees can choose the type of configuration to store and/or restore email messages. If this mechanism is not configured, email messages are stored and/or restored in the rich text format.

Configuring the IMCM.rss file

Set the store_plain_body_text field to any of the following values at the client-side. This value is used to configure the IMAP and POP3 MTMs to decide the type of storage to be used for storing email messages.

  1. Locate the IMCM.rss file at the messaging\email\clientmtms\group location.

  2. Set the value of the store_plain_body_text field to any of the following values:

    Value Description


    To store the body text of an email message in chunks when messages are downloaded through IMAP and POP3.

    This is the default value.


    To store the entire body text of an email message in the RAM when messages are downloaded through IMAP and POP3.