/**
  * Wrap an unstructured header line
  *
  * Wrap at 78 characters or before, based on whitespace.
  *
  * @param string          $value
  * @param HeaderInterface $header
  * @return string
  */
 protected static function wrapUnstructuredHeader($value, HeaderInterface $header)
 {
     $encoding = $header->getEncoding();
     if ($encoding == 'ASCII') {
         return wordwrap($value, 78, Headers::FOLDING);
     }
     return static::mimeEncodeValue($value, $encoding, 78);
 }