Fatal error: Uncaught Error: Class 'Symfony\Component\Mime\Part\AbstractMultipartPart' not found in C:\xampp\htdocs\plugins\Symfony\Component\Mime\Part\Multipart\AlternativePart.php:19 Stack trace: #0 {main} thrown in C:\xampp\htdocs\plugins\Symfony\Component\Mime\Part\Multipart\AlternativePart.php on line 19