public function addBlobAttachment($content, $filename, $mimeType = null, $fileInfo = []) {
		if ($mimeType === null) {
			$ext = pathinfo($filename, PATHINFO_EXTENSION);
			$mimeType = $this->_getMimeByExtension($ext);
		}
		$fileInfo['data'] = $content;
		$fileInfo['mimetype'] = $mimeType;
		$file = [$filename => $fileInfo];
		return $this->addAttachments($file);
	}