Folgende Probleme sind bei einem Update von 9 -> 10 aufgetreten

Fehlermeldung

Symfony\Component\Mime\Message::setBody(): Argument #1 ($body) must be of type ?Symfony\Component\Mime\Part\AbstractPart, string given,

Lösung

Statt

$message = $this->objectManager->get('TYPO3\\CMS\\Core\\Mail\\MailMessage'); 
$message->setTo([$this->settings['to']])
    ->setFrom([$this->settings['from_email'] => $this->settings['from_name']])
    ->setSubject($this->settings['subject']); 
$message->setBody('text/html', $emailBody); 

die setBody wie folgt aufrufen:

$message = $this->objectManager->get('TYPO3\\CMS\\Core\\Mail\\MailMessage'); 
$message->setTo([$this->settings['to']])
    ->setFrom([$this->settings['from_email'] => $this->settings['from_name']])
    ->setSubject($this->settings['subject']); 
$message->setBody()->html($emailBody);