Post SMTP plugin require at least PHP version 5.6, contact to your web hostig support to upgrade.
See supported versions on PHP.net
'; if ( isset( $_GET['activate'] ) ) { unset( $_GET['activate'] ); } } function post_smtp_plugin_admin_notice() { echo 'Post SMTP plugin is a fork (twin brother) of the original Postman SMTP, you must disable Postman SMTP to use this plugin.