(integer) When converting a multi-part email message to an SMS message, only the first MAX_MESSAGE_PARTS number of text parts will be converted. The remaining parts are discarded. By default, MAX_MESSAGE_PARTS is 2. To allow an unlimited number of message parts, specify a value of -1. When a value of 0 is specified, then no message content will be placed into the SMS message. This has the effect of using only header lines from the email message (for example, Subject:) to generate the SMS message.
Note that an email message containing both text and an attachment will typically consist of two parts. Note further that only plain text message parts are converted. All other MIME content types are discarded.