By default, e-mail messages that you receive from people who are listed in your Contacts are considered safe by the Junk E-mail Filter. However, the people in your Contacts are not literally added to the Safe Senders List unless you send e-mail to a contact while you have the Automatically add people I e-mail to the Safe Senders List check box selected.
To change this setting, do the following:
On the Tools menu, click Options.
On the Preferences tab, under E-mail, click Junk E-mail.
Click the Safe Senders tab.
Select or clear the Also trust e-mail from my Contacts check box.