public function setFile(Swift_FileStream $file, $contentType = null)
    {
        $this->setFilename(basename($file->getPath()));
        $this->setBody($file, $contentType);
        if (!isset($contentType)) {
            $extension = strtolower(substr($file->getPath(), strrpos($file->getPath(), '.') + 1));

            if (array_key_exists($extension, $this->mimeTypes)) {
                $this->setContentType($this->mimeTypes[$extension]);
            }
        }

        return $this;
    }