private function AddSmtpSecurityField()
    {
        $name = 'SmtpSecurity';
        $field = new Select($name, $this->settings->GetSmtpSecurity());
        $values = SmtpSecurity::AllowedValues();
        foreach ($values as $value)
        {
            $field->AddOption($value, Trans("Core.SettingsForm.SmtpSecurity.$value"));
        }
        $this->AddField($field);
    }