You can mark an email address as a Safe Sender by doing the following:
Go to Outlook & click the Home tab at the top of the screen.
Select Junk > then Junk E-Mail Options…
This will open a new window. Click on the tab called Safe Senders > Then click Add > Then enter the email address you want to add as a Safe Sender. Then click Apply.
Then all emails from that email address will come into your mailbox.