Your ISP (Internet Service Provider) may restrict your outgoing mail, requiring you to use their outgoing mail server. You can contact your ISP to get the correct outgoing server name.
If you are using Outlook 2002 (aka Outlook XP), you must upgrade to Outlook service pack 3 in order to send mail using the AKO/DKO outgoing mail server. You can download this from the Outlook support homepage at http://support.microsoft.com/ph/2559
You may also have anti-virus or firewall software that is interfering with the operation of your Email Client. Please ensure you close these programs fully (instead of simply disabling them) if you are experiencing issues.