Fatal error: Uncaught Error: Interface 'Symfony\Component\Mime\Header\HeaderInterface' not found in /home/devmecseminars/public_html/mec/vendor/symfony/mime/Header/AbstractHeader.php:21 Stack trace: #0 {main} thrown in /home/devmecseminars/public_html/mec/vendor/symfony/mime/Header/AbstractHeader.php on line 21