$mail_body = preg_replace('@\r?\n@', $line_endings, $message['body']);
// For headers, PHP's API suggests that we use CRLF normally,
// but some MTAs incorrectly replace LF with CRLF. See #234403.
- $mail_headers = join("\n", $mimeheaders);
+ $mail_headers = implode("\n", $mimeheaders);
$request = \Drupal::request();