Immediately after Windows updates today on 2 different systems, so far, you cannot open Outlook. As soon as you open it closes. Next time you open you get the Open Outlook In Safe mode popup, which also doesn’t work. After looking at commonalities in the two systems and trouble shooting it seems the issue was the July 14th ‘Patch Tuesday’ update “Cumulative Update for Windows 10 Version 1909 for x64-based Systems (KB4565483)”. The update includes multiple features but among them is “Updates to improve security when using Microsoft Office products.” Uninstalling the update immediately resolved the issue.
If unfamiliar with doing so go to Control Panel, click on “Programs and Features”, then “View installed updates”, locate the (KB4565483) Update, right click and choose uninstall. As always you should have a backup of your system before adding or removing updates.
I have also selected “pause updates for 7 days” in case it tries to reinstall before Microsoft has a fix.
Update: It seems this does not always work. Instead you need to roll back Office, however Microsoft has apparently realized the problem and is pushing out the fix. To enforce, just close Outlook and re-open. This worked on the latest machine with which I had a problem and there was a message in Outlook about the issue when it did open. It may not be pushed out to all machines yet so waiting a couple of hours may be necessary. See the following link from Microsoft regarding details: https://support.microsoft.com/en-us/office/active-investigation-into-outlook-crashing-on-launch-9c59ad4b-813c-432a-afdc-f14717a4528d?ui=en-us&rs=en-us&ad=us