Correction:
in C:\xampp\htdocs\wp\wp-includes\class-phpmailer.php on line 1023

Fatal error: Uncaught phpmailerException: Invalid address: (setFrom) in C:\xampp\htdocs\wp\class-phpmailer.php:1023 Stack trace: #0 C:\xampp\htdocs\wp\wp-includes\pluggable.php(352): PHPMailer->setFrom('', 'Oliver Travel T...', false) #1 C:\xampp\htdocs\wp\wp-content\plugins\wpforo\wpf-includes\wpf-hooks.php(1322): wp_mail('', 'New Topic', 'Hello !<br>\r\n N...', Array) #2 C:\xampp\htdocs\wp\wp-includes\class-wp-hook.php(298): wpforo_forum_subscribers_mail_sender(Array) #3 C:\xampp\htdocs\wp\wp-includes\class-wp-hook.php(323): WP_Hook->apply_filters(false, Array) #4 C:\xampp\htdocs\wp\wp-includes\plugin.php(453): WP_Hook->do_action(Array) #5 C:\xampp\htdocs\wp\wp-content\plugins\wpforo\wpf-includes\class-topics.php(141): do_action('wpforo_after_ad...', Array) #6 C:\xampp\htdocs\wp\wp-content\plugins\go2wpforo\migrate2wpforo.php(256): wpForoTopic->add(Array) #7 C:\xampp\htdocs\wp\wp-content\plugins\go2wpforo\includes\fun in C:\xampp\htdocs\olivertt-www\wp-includes\class-phpmailer.php on line 1023

Do you have any idea what the problem could be?

I have tried to run this on PHP 7.1, 7.0 and 5.6 with all the same problem. WP Version 4.7.3.