To add to your Safe-Sender's List, please follow the steps below:

1. Start by selecting 'Tools' from the top menu and then 'Junk E-mail Options' from the drop-down list.
2. If you get a fair bit of spam and are willing to put up with the occasional legitimate email being marked as Junk (which is called a false-positive), you might want to switch to the High level of filtering. If you choose the high setting, be sure to check your Junk E-mail folder fairly often to make sure no actual messages were incorrectly flagged. Also, it's a very good idea not to permanently delete suspected junk e-mail instead of moving it to the junk email folder, because there's a very good chance you'd be automatically deleting messages that are not spam. 

The final option is to only accept email from people (or domains like gmail.com) that you specify (your safe senders list). Only use this option if you know exactly who will be sending you email messages.

1. Select the 'Safe Senders' tab. One default setting that you might want to change is the 'Automatically add people I e-mail to the Safe Senders List', which is turned off by default.
2. And finally, select the 'Phishing' tab. Microsoft has included anti-phishing (more info on phishing here filters as a part of Windows Mail. You may wish to place a check in the box labeled 'Move phishing E-mail to the Junk Mail folder', but be sure to check your Junk Mail folder once in a while for false-positives.
3. If you find that Windows Mail has incorrectly identified a message as spam, and your settings are such that Junk mail is moved to the Junk folder, use the 'Not Junk' button to restore messages to the Inbox.