Icons in Outlook WebAccess in Office 365 not rendering

Question

Good afternoon,

We have recently received reports of people connecting to webmail and when it opens, the icons for Mail, Calendar, Contacts don't render correctly. Neither do your email actions such as Reply, reply to All. Settings icon is not rendering. they just show as a blank rectangle. There is a screenshot attached for reference. We have only had a few reports, but are curious if anyone might have insight as to what might be the issue. Had another use check and she did not have the issue, so there does not seem to be common thread.

Thank You

Answer 1

Our issue was due to a block on our web proxy. It was not allowing for all sites to pass through. Our case with Microsoft told us to check the following *.cloud.microsoft.com, *.static.microsoft.com, *.usercontent.microsoft.com and res.public.onecdn.static.microsoft on ports 80 and 443. Provided a link to Office 365 URLs Microsoft 365 URLs and IP address ranges - Microsoft 365 Enterprise | Microsoft Learn

People who support our web proxy ended having to add outlook.cloud.microsoft and

*.onecdn.static.microsoft to our webmail allowed list, and when I refreshed the problem went away.  

You could have your folks who support firewalls or proxies check this as well. This seems to have corrected the issue for our users.

Thank You

 

Answer 2

My 2 euro-cents:

Check if you have any extension (like Greasemonkey, Stylus etc) that affects the CSS stylesheets. This could also be any other extension that changes the look of your browser, but also "security" apps like antivirus or similar.

Windows 7 - 11 are perfectly secure without any of these so that you can safely disable them.