Assuming you are using Outlook 2003, try the menu bar: Tools > Options >
Preferences > Junk Mail > International then click on "Blocked top-level
Domain list... You can check the countries you do not want to receive
E-mail from and uncheck the ones that you do want to receive E-mail from.
You can also enter the URL or E-mail address for each sender in the Blocked
Senders area as you receive them. They will be routed to your Junk-mail
folder thereafter.