Extension points

Recipients

interface Recipients
{
    /** @return non-empty-list<string> */
    public function for(ContactMessage $message): array;
}

ConfiguredRecipients gives the configuration's addresses. An application whose pages write to different people — an organisation of a directory, a shop of a network — replaces the alias Recipients with its own service, which reads, for instance, the request or a field it adds to the form.

The form elsewhere

ContactFormType and ContactMailer are services: a controller of the application builds the form, handles it and sends $form->getData() with ContactMailer::send(), in a page of its own design.