Fatal error: Uncaught Error: Class 'Symfony\Component\Mime\Header\UnstructuredHeader' not found in C:\Apache24\htdocs\InvoiceTracking\vendor\symfony\mailer\Header\TagHeader.php:19 Stack trace: #0 {main} thrown in C:\Apache24\htdocs\InvoiceTracking\vendor\symfony\mailer\Header\TagHeader.php on line 19