Fatal error: Uncaught Error: Class "Symfony\Component\Mime\Part\AbstractMultipartPart" not found in C:\Apache24\htdocs\cms_upgrade\vendor\symfony\mime\Part\Multipart\MixedPart.php:19 Stack trace: #0 {main} thrown in C:\Apache24\htdocs\cms_upgrade\vendor\symfony\mime\Part\Multipart\MixedPart.php on line 19