Missign usage of $reply_to in function sendMailPhpMailer()

[PMautry]

In the versions 3.6.16 and 3.7.0RC, the variable $reply_to is set in lib.php function sendMailPhpMailer(...), but never used.

Please consider adding

    if (USE_REPLY_TO) {
        $mail->addReplyTo($reply_to);
    }

before the call of $mail->compatSend(...)

I found this while digging with DMARC issues and hope, I could help a little bit.

Thank you for your work on phpList!

Best regards,
Patrick Mautry