protected function validateEmailAsPdfFields()
    {
        // Check for valid email address if no token syntax is used.
        $regexpEmail = '/^[^@<>,; "\']+@([^.@ ,;]+\.)+[^.@ ,;]+$/';
        if (!empty($this->submittedValues['emailTo']) && strpos($this->submittedValues['emailTo'], '[') === false && !preg_match($regexpEmail, $this->submittedValues['emailTo'])) {
            $this->errorMessages['emailTo'] = $this->t('message_validate_email_5');
        }

        // Check for valid email addresses if no token syntax is used.
        $regexpMultiEmail = '/^[^@<>,; "\']+@([^.@ ,;]+\.)+[^.@ ,;]+([,;][^@<>,; "\']+@([^.@ ,;]+\.)+[^.@ ,;]+)*$/';
        if (!empty($this->submittedValues['emailBcc']) && strpos($this->submittedValues['emailBcc'], '[') === false && !preg_match($regexpMultiEmail, $this->submittedValues['emailBcc'])) {
            $this->errorMessages['emailBcc'] = $this->t('message_validate_email_3');
        }

        // Check for valid email address if no token syntax is used.
        if (!empty($this->submittedValues['emailFrom']) && strpos($this->submittedValues['emailFrom'], '[') === false && !preg_match($regexpEmail, $this->submittedValues['emailFrom'])) {
            $this->errorMessages['emailFrom'] = $this->t('message_validate_email_4');
        }
    }