Follow these steps to configure MS Outlook to access MS Exchange server when client computer is not on a local network.

1.    Close MS Outlook
2.    Start > Settings > Control Panel > Mail > Show Profiles > Add (if you don’t see “Mail” icon in Control Panel click “Switch to Classic View” on left hand side)
3.    Name new profile “Outlook” and click OK
4.    Select “Manually configure server settings…” > Next
5.    Select “Microsoft Exchange…” Next
Server: <servername>
Use Exchange Cashed Mode: Yes
User Name: <user.name>
6.    Click “More Settings”
7.    Click “Connection” Tab
8.    Sect “Connect to Microsoft Exchange using HTTP”
9.    Click “Exchange Proxy Settings”
Use this URL to connect…: <Outlook Web Access URL>
Connect Using SSL only: Yes
On fast networks , connect using HTTP first: Yes
On slow networks, connect using HTTP first: Yes
Proxy authentication settings:  Basic Authentication
OK > OK > Next

10.    Enter username: <domain\user.name> and <domain password>
11.    Click Finish
12.    In Mail box (from step 2) – “Always use this profile” select “Outlook”
13.    OK
14.    Open Outlook

Outlook 2010
Windows XP
Exchange 2007