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