This answer comes from the Microsoft Supportability e-newsletter: http://blogs.technet.com/asiasupp/default.aspx?p=3
1. Create a share folder on server, say Junk E-mail, and give everyone read permission. Create a text file name SafeSender.txt. Input email addresses into file (one address one line).
2. Install "Microsoft Office 2003 Resource Kit" on the Domain Controller.
3. Start Active Directory Users and Computers (ADUC), Right Click on the OU in which users account is present, Go To "Properties", Click on "Group Policy" tab.
4. Select the Policy in effect, click on "Edit". It will open "Group Policy Object Editor". Right click on "Administrative Templates" under "User Configuration" -> All Tasks -> "Add/Remove Templates" -> Click on "Add" -> Select "Outlk11.ADM" and click "Open" -> Click "Close".
5. Expand "Microsoft Office Outlook 2003" under "Administrative Templates" -> Expand "Tools Options" -> Expand "Preferences" -> Click on "Junk E-mail".
6. In the right pane double click on "Specify path to Safe Senders list".
7. Click on "Enabled" and under "Specify full path and filename to Safe Senders list" type UNC path of SafeSender.txt file (e.g.\\Server\JunkE-mail\SafeSenders.txt).
8. Double Click "Overwrite/Append Junk Email Import List" to configure if you want to keep user's own list.
9. Click on OK. Close "Group Policy Object Editor". Click OK again. Close Active Directory Users and Computers.
10. Log on to client machine and edit the following registry entry:
DWORD = JunkMailImportLists
Value = 1
Note: This registry key should be deployed to the client machines for successfully deploying the Safe Senders List. We can use Group policy again to deploy this key. The value of this registry key will turn back to zero after Outlook applies the safe sender list from group policy. So if you need to modify the list, please change the value to 1 again.
11. Log off from the client machine and log on again.
12. Launch Outlook. Now you can see the email addresses in the Safe Sender list.
NOTE: The same procedure described above can be used to specify "Safe Recipients" and "Blocked Senders" list.
We also can use the Custom Installation Wizard or the Custom Maintenance Wizard to deploy such lists. Please refer to the following article for more information.
How to use the Custom Installation Wizard or the Custom Maintenance Wizard to customize user profiles to load default junk e-mail filter lists in Outlook 2003
Class: Information Worker: Outlook 2007 Power User*
Date: November 12, 2008
Location: Indiana State University
*The Information Worker series is available through LanTech Training in Indianapolis. Please visit their website for more information