protected function encodeHeader($str) {
		if (extension_loaded('iconv')) {
			$out = iconv_mime_encode('Subject', $str,
				['input-charset' => 'UTF-8', 'output-charset' => $this->charset]);
			$out = substr($out, strlen('Subject: '));
		} elseif(extension_loaded('mbstring')) {
			mb_internal_encoding('UTF-8');
			$out = mb_encode_mimeheader($str, $this->charset, 'B', static::$EOL, strlen('Subject: '));
		} else
			$out = wordwrap($str,65,static::$EOL);
		return $out;
	}