Yes. In the web filter, the Blanket Block function allows to completely block web surfing except for those domains/urls added to the White List.
Is it possible to import the WebURL list in your Protector which i want to white list for O365 usage? Microsoft has a complete URL List in XML format. Please see following link.
I's a matter of white listing in the web filter , it's possible to upload a list in csv format.
To block everything the easiest thing is to use the blanket block.
Then the Office 365 IPs must be added to the white list.