Fatal error: Uncaught Error: Class "Symfony\Component\Mime\Header\UnstructuredHeader" not found in /srv/www/sites/public/starter-cms/vendor/symfony/mailer/Header/MetadataHeader.php:19 Stack trace: #0 {main} thrown in /srv/www/sites/public/starter-cms/vendor/symfony/mailer/Header/MetadataHeader.php on line 19