Fatal error: Uncaught Error: Interface 'Drupal\Core\DependencyInjection\ServiceProviderInterface' not found in /var/www/html/tmp/contrib/mailsystem/src/MailsystemServiceProvider.php:13 Stack trace: #0 {main} thrown in /var/www/html/tmp/contrib/mailsystem/src/MailsystemServiceProvider.php on line 13