public function setContent($data, $mime, $charset=NULL) {
		if (!$charset)
			$charset=$this->charset;
		$this->message[$mime] = [
			'content'=>$data,
			'type'=>$mime.'; '.$charset
		];
	}
public function setContent($data, $mime, $charset=NULL) {
		if (!$charset)
			$charset=$this->charset;
		$this->message[$mime] = [
			'content'=>$data,
			'type'=>$mime.'; '.$charset
		];
	}
public function setContent ( $ data , $ mime , $ charset = NULL ) { if ( ! $ charset ) $ charset = $ this -> charset ; $ this -> message [ $ mime ] = [ 'content' => $ data , 'type' => $ mime . '; ' . $ charset ] ; }
set message contents by mime type
@param string $data message data
@param string $mime the mime type
@param null $charset
set message contents by mime type