These are the common errors made by most clients...
- You do not tick the option "My outgoing mail server requires authentication". If you do, make sure you are using the same settings as your incoming mail server. Please refer to these articles on "How do I setup my email account in Outlook Express?" and "How do I setup my email account in Microsoft Office Outlook?".
- You are using port number 25 for your outgoing mail server. Try change it to 587 (for Malaysia server) or 26 (for overseas server). Most probably your ISP has block port number 25. Please refer to here for more instructions.