Moses,
If you are running an Exchange server on the other end, you might need to use the 'Outlook Anywhere' feature which enables the client to communicate with the Exchange Server over a HTTP tunnel.
The Microsoft support site says:
Enable Outlook Anywhere in Outlook
- On the Tools menu, click Account Settings, select the Exchange account, and then click Change.
- Click More Settings, and then click the Connection tab.
- Under Outlook Anywhere, select the Connect to Microsoft Exchange using HTTP check box.
Check it out and let us know if it works.
Kind regards,
Bernard