Make sure you have the home / mail server set in your location document.
At the bottom right hand corner of the screen there will be a grey box with "Office" or another similar word written in it, click on it and select "Edit Current". Find the field that says home server and enter your home server's name if you know it or the name of the server you use the most as a rough guess.
You can find out the correct home/main server by opening the main name and address book, (names.nsf on any server), and then looking at your record.