Microsoft Office 365 and Office 2013 have a problem authenticating thru a proxy so you will need to add the following domains to "Authentication Exceptions".
UPDATED - February 13, 2020
1. Add all addresses from the list below to Authentication Exceptions:
Website Filtering > Authentication Exceptions > Add A Site
Site IP or Net Address: office365.com
Reason for Change: Allow Office 365
Submit
2. Add all addresses from the list below to the Allowed Site List
Website Filtering > Website Access > Add A Site
Website Address: office365.com
Reason For Change: Allow Office 365
Filtering: Unfiltered
Port Access: Check
Select all Filter Sets that will be using Office 365
Repeat the above steps for the following list of domains:
- office365.com
- outlook.com
- microsoft.com
- office.com
- office.net
- msn.com
- msn.co.jp
- msn.co.uk
- sharepoint.com
- live.com
- live.net
- msecnd.net
- msocdn.com
- microsoftonline.com
- microsoftonline-p.com
- microsoftonline-p.net
- microsoftonlineimages.com
- microsoftonlinesupport.net
- lync.com
- aadrm.com
- activedirectory.windowsazure.com
- onmicrosoft.com
- phonefactor.net
- sharepointonline.com
- office.net.akadns.net
- edgesuite.net
- msedge.net
- skype.com
- f-msedge.net
- onestore.ms
- azure.net
- azureedge.net
- bing.net
- trafficmanager.net
- onedrive.com
- sfx.ms
- akamaihd.net
- svc.ms
- skypeforbusiness.com
- sfbassets.com
- windows.net
- windows.com
- aspnetcdn.com
- mstea.ms
- skypeassets.com
- onenote.com
- atdmt.com
- aspnetcdn.com
- optimizely.com
- onedrive.com
- msappproxy.net
- msftidentity.com
- msidentity.com
- msauth.net
- msauthimages.net
- msft.net
- cloudappsecurity.com
- helpshift.com
- localytics.com
- oaspapps.com
- uservoice.com
- akadns.net
- o365weve.com
- cloudapp.net
- Optional - autodiscover.local domain (ex. autodiscover.xyz.local)
Commit Changes and Restart Services when finished.