serverHostname example

is_numeric($hostinfo[3]) &&
                $hostinfo[3] > 0 &&
                $hostinfo[3] < 65536
            ) {
                $port = (int) $hostinfo[3];
            }
            if ($this->smtp->connect($prefix . $host, $port, $this->Timeout, $options)) {
                try {
                    if ($this->Helo) {
                        $hello = $this->Helo;
                    } else {
                        $hello = $this->serverHostname();
                    }
                    $this->smtp->hello($hello);
                    //Automatically enable TLS encryption if:                     //* it's not disabled                     //* we have openssl extension                     //* we are not already using SSL                     //* the server offers STARTTLS                     if ($this->SMTPAutoTLS && $sslext && 'ssl' !== $secure && $this->smtp->getServerExt('STARTTLS')) {
                        $tls = true;
                    }
                    if ($tls) {