Configuring Microsoft Outlook Express
1. Open Outlook Express.
2. Click on 'Tools | Accounts...'.
3. Click on the 'Mail' tab.
4. On the right side, click on 'Properties'.
5. Now click on the 'Servers' tab.
Make sure the POP Logon name is the same as the Account name (username) that is used by mail clients when they connect to the server to retrieve email. Eg: mailbox@postoffice.
If you have enabled SMTP Authentication on your server, you should check the option instructing Outlook Express that your outbound server requires authenticaton. The checkbox to do this is labelled My server requires authentication.
For assistance in setting up other mail clients, please refer to the MailEnable web site.