Are you sure your company has Web Service for Exchange configured? This is in the System Setup guide on page 13:
Setting system preferences
In the System Preferences window, you can set home page defaults, enable the
option for users to automatically log in to Microsoft Dynamics GP, and specify the
location of your Microsoft SharePoint®.
To set system preferences:
1. Open the System Preferences window.
(Administration >> Setup >> System >> System Preferences)
2. Enter the URL for your SharePoint server so that you can use the search box in
Microsoft Dynamics GP.
3. Select MAPI or Exchange as your email server type.
If you select Exchange, you must be using Exchange 2007 Service Pack 1 or
greater with Exchange Web Services. The Autodiscover service must be enabled
to connect to the Exchange server.