Using v3.6.1

Fatal error: Uncaught Error: Call to a member function createMailEngine() on null in /home/xxx/webapps/xxx/wp-content/plugins/post-smtp/Postman/PostmanWpMail.php:202 Stack trace: #0 /home/xxx/webapps/xxx/wp-content/plugins/post-smtp/Postman/PostmanWpMail.php(60): PostmanWpMail->sendMessage() #1 /home/xxx/webapps/xxx/wp-content/plugins/post-smtp/Postman/PostmanWpMailBinder.php(149): PostmanWpMail->send() #2 /home/xxx/webapps/xxx/wp-content/plugins/wordfence/lib/wordfenceClass.php(1956): wp_mail() #3 /home/xxx/webapps/xxx/wp-includes/class-wp-hook.php(324): wordfence::veryFirstAction() #4 /home/xxx/webapps/xxx/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() #5 /home/xxx/webapps/xxx/wp-includes/plugin.php(517): WP_Hook->do_action() #6 /home/xxx/webapps/xxx/wp-settings.php(578): do_action() #7 /home/xxx/xxx/xxx/wp-config.php(45): require_once(‘…’) #8 /home/xxx/webapps/xxx/wp-load.php(50): require_once(‘…’) #9 /home/xxx/webapps/xxx/wp-blog-header.php(13): require_once(‘…’) #10 /home/xxx/webapps/xxx/index.php(17): require(‘…’) #11 {main} thrown in /home/xxx/webapps/xxx/wp-content/plugins/post-smtp/Postman/PostmanWpMail.php on line 202