A given MIME compliant message in string form can be used to
reconstruct a Zend_Mime_Message Object from it.
Zend_Mime_Message has a static factory Method to parse this
String and return a Zend_Mime_Message Object.
Zend_Mime_Message::createFromMessage($str, $boundary)
decodes the given string and returns a Zend_Mime_Message
Object that can then be examined using getParts()