Fatal error: Uncaught Error: Class "Symfony\Component\Mime\Header\UnstructuredHeader" not found in /home/bimmertest/BookStack/vendor/ssddanbrown/symfony-mailer/Header/TagHeader.php:19 Stack trace: #0 {main} thrown in /home/bimmertest/BookStack/vendor/ssddanbrown/symfony-mailer/Header/TagHeader.php on line 19