PHP Problem

Hello
I am getting an error like the one below. I couldn’t find the source of this problem. Can you help? Thanks

Fatal error: Uncaught Error: Call to undefined function php_uname()
in /home/zettdekor/public_html/wp-content/plugins/smtp-mailer/main.php on line 221

Call stack:

1. SMTP_MAILER::server_info_settings()
   wp-content/plugins/smtp-mailer/main.php:145
2. SMTP_MAILER::options_page()
   wp-includes/class-wp-hook.php:324
3. WP_Hook::apply_filters()
   wp-includes/class-wp-hook.php:348
4. WP_Hook::do_action()
   wp-includes/plugin.php:517
5. do_action()
   wp-admin/admin.php:259
6. require_once()
   wp-admin/options-general.php:10