Add docs

src/Monolog/Handler/MailHandler.php

@@ -40,7 +40,7 @@ abstract class MailHandler extends AbstractProcessingHandler
     /**
      * Send a mail with the given content
      *
-     * @param string $content
+     * @param string $content formatted email body to be sent
      * @param array  $records the array of log records that formed this content
      */
     abstract protected function send($content, array $records);