If you would like to add an individual sender (firstname.lastname@example.org) or sender's domain (like @example.com) to your Safe Senders list in Outlook, you can quickly accomplish this task with the following steps:
1) From the Home menu, navigate to Junk > Junk Email Options
2) Click the Safe Senders tab and then click Add...
3) Type in the sender's email address or domain name and click Ok.
4) Additionally, you can check boxes to trust e-mail from your Contacts and/or automatically add people that you email to the Safe Senders list.