PHPMailer::setSMTPXclientAttribute( string $name, PHPMailer\PHPMailer\?string $value ): bool

2192    public function setSMTPXclientAttribute($name, $value)2193    {2194        if (!in_array($name, SMTP::$xclient_allowed_attributes)) {2195            return false;2196        }2197        if (isset($this->SMTPXClient[$name]) && $value === null) {2198            unset($this->SMTPXClient[$name]);2199        } elseif ($value !== null) {2200            $this->SMTPXClient[$name] = $value;2201        }2202 2203        return true;2204    }