After updating to Safari 13.0.3 Outlook.com cannot display emails

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If I use Google Chrome or Firefox, I don’t have the problem. If I access my personal email @outlook.com in Safari 13.0.3 on Mojave, I don’t have the problem. If I use Safari 13.0.3 on Catalina for the same scenario, I don’t have the problem. 

To better define what I see/experience, I login to either https://login.microsoftonline.com or https://login.live.com. Once logged in, I have access to the apps for Office 365. I am able to get in and work on Word, Excel, Powerpoint, etc. , except for Outlook.

Once I click on Outlook, I get prompted for Duo authentication as I should for our systems. I click on “Send Me a Push”, then approve it on my iPhone.

At this point, I’m already logged on to the Office 365 website, so the authentication has moved pass Duo and is being passed from Duo back to Microsoft. Now, If I don’t get in to Outlook, I get this indication that “We couldn’t sign you in”, yet under my account name it shows as being Signed In (Office 365).

But if I DO get into Outlook, It lists my emails in the Inbox, including anything new, but the preview pane will not display the email. If I double-click an email it opens it up in a new window. If I click the preview pane or any folder other than the Inbox, it won’t display anything. It’s like it initially talks to the email server, but then loses the connection. I can still access Word or Excel.

I’ve tried clearing the Safari cache, signing out and forgetting the account, booting into Safe mode (no 3rd party interference), clear system, user, and font caches, but none of it resolves the problem. This is only on Mojave only with Safari 13.0.3.

Re-imaged a Mac with 10.14.6 (18G103 ). No enrollment or modifications. New clean image includes Safari 12.1.2, which worked as it should.

Installed Security Update 2019-001. The build is 10.14.6 (18G1012 ). Safari is still 12.1.2 (14607.3.9). Was able to access Outlook via OWA without a problem.

Updated to Safari 13.0.3 (14608.3.10.10.1) and I now have the problem. There is no anti-malware, no enrollment, just a clean Apple macOS 10.14.6 with the Security update and the Safari Update.

The problem exists specifically when Safari 13 is installed on macOS Mohave 10.14.6. And no, it doesn't work in Safe mode, which is consistent with what I find with a clean OS install.

Yeah, I was thinking of that, but am going to explore a few other things. We're thinking it might be an iFrame issue, because I can open an email from the inbox if I double click it. I've also checked out the network communication via Safari's developers options. I find a server response code of 449. In Wireshark, I can see the request for the certificate & handshake and the receipt of the certificate and a completed handshake.

So, here’s a weird update on my original post. One strange observation is when Outlook.com is opened In Safari 13.0.3 on my iMac (or MacBook Pro) running Mojave 10.14.6 I still see “Message cant’ be opened right now....” with no display of emails. The circle where my photo normally occurs, in top right upper corner, shows only my initials on a bright red background (never seen that before). If I click that red circle, it gives me an option to “open another mailbox”. I tried that, it shows a box to enter an email address, and put in the SAME address just used to open Outlook the first time...no changes. Voila! It opens a new tab but this time the right panel displays my email content as it’s supposed to. I can switch back and forth between the two tabs, or simply close out the first (inoperative) tab and proceed as if nothing is wrong...except the red circle remains with my initials. If I open Outlook.com in Firefox, that red circle is replaced by my familiar photo, as before, but not when running in Safari. So, try opening another mailbox window or tab for now, until the next Safari or Outlook update corrects this strange issue.

I am proposing a workaround, not a fix. When I have seen these behaviors, changing the User Agent to Microsoft Edge and clearing the browser cache seems to resolve it...until you close Safari. Safari's default User Agent string is fixed and can be altered, although at this time, I haven't quite been able to make this happen. I would be interested to hear if any others have done this already and found it effective.

You could reinstall Mojave to get Safari 12 back.

That actually worked! Thanks, nutdr! Wow, that suggests something in the initial communication is out of order or just being acknowledged. This is a strange bug. Thanks, much appreciated!