Cannot Activate

Cannot Activate due to error:

Fatal error: Uncaught TypeError: array_merge(): Argument #1 must be of type array, string given in /var/www/wp-content/plugins/post-smtp/Postman/PostmanInstaller.php:44 Stack trace: #0 /var/www/wp-content/plugins/post-smtp/Postman/PostmanInstaller.php(44): array_merge('o', Array) #1 /var/www/wp-content/plugins/post-smtp/Postman/Postman.php(127): PostmanInstaller->activatePostman() #2 /var/www/wp-content/plugins/post-smtp/postman-smtp.php(176): Postman->__construct('/var/www/wp-con...', '2.1.10') #3 /var/www/wp-content/plugins/post-smtp/postman-smtp.php(167): post_setupPostman() #4 /var/www/wp-content/plugins/post-smtp/postman-smtp.php(96): post_smtp_start(51075152) #5 /var/www/wp-admin/includes/plugin.php(2313): include_once('/var/www/wp-con...') #6 /var/www/wp-admin/plugins.php(192): plugin_sandbox_scrape('post-smtp/postm...') #7 {main} thrown in /var/www/wp-content/plugins/post-smtp/Postman/PostmanInstaller.php on line 44