Hello,
Can you please explain what triggered the email (without subject) sent by PayPlan?
The content is only warnings:
Warning: include(Array): failed to open stream: No such file or directory in /administrator/components/com_payplans/includes/mailer/mailer.php on line 106
Warning: include(): Failed opening 'Array' for inclusion (include_path='.:/usr/local/php71/pear') in /administrator/components/com_payplans/includes/mailer/mailer.php on line 106