Running Windows 2003 Small Business Server for Exchange purposes only. Most client computers are not connected to the domain as they may be members of other domains and work offsite. Otlook clients can connect to the Exchange server when they are connected to local network. Using Outlook Web Access from remote location with web browser works with both HTTP and HTTPS, despite the certificate warning as it is not issued by a trusted authority.
However, the Outlook clients are not able to connect to the server when they are outside using Outlook HTTP connection.