How to add email addresses to the Safe Senders list and Blocked Senders list in OWA 2013

On the main page of OWA, select the gear icon at the top right of the page and select Options. From the left hand pane of the Options panel, select Block or Allow.

From here you can add the desired sender or domain to the Safe Senders list or Blocked Senders list by entering in the name and selecting the add icon. Once all of the entries are added, scroll down to the bottom of the page and select Save.