* @self: a #ModestFormatter
* @part: a non-NULL #TnyMimePart with the body of the original message
* @header: a non-NULL #TnyHeader of the original message
* @self: a #ModestFormatter
* @part: a non-NULL #TnyMimePart with the body of the original message
* @header: a non-NULL #TnyHeader of the original message