Problem may occur because your router does not support TCP Window Scaling, which is a new windows vista feature.
You may get "sending\receiving error (0x800CCC0F), please contact your system administrator".

Fix it in two ways:
Download and install microsoftfix50056.msi

1. Login to your computer as administrator.
2. Go to start < run < type "cmd" and press OK.
3. On the command line type the following string:
netsh interface tcp set global autotuninglevel=disabled
4. Press Enter.
5. Restart outlook.