OJS 3.1.2-4 not sending any email

And, since you’re already looking at the PHPMailer debugging info, you can add this line to lib/pkp/classes/mail/Mail.inc.php

            $mailer->SMTPDebug = SMTP::DEBUG_CONNECTION;

Right after this line:

            $mailer = new \PHPMailer\PHPMailer\PHPMailer();

in the send() method.

That should dump out fair amount of debugging information.

Cheers,
Jason