We last reported about many Windows 10 version 2004 and version 1909 users facing issues with Outlook after installing the updates KB4565503 and KB4565483. Now, not only Microsoft acknowledged this issue it has also claimed to fix this issue.

On its official update page, Microsoft has provided all the details about this issue and how it has been resolved. Microsoft expects the resolution to be available for everyone using Outlook already.

Outlook closes unexpectedly or you might receive an error when attempting to open

Microsoft Outlook might close unexpectedly or you might receive an error when attempting to open the app. An example of an error you might receive is, “Outlook couldn’t start last time. Safe mode could help you troubleshoot the problem, but some features might not be available in this mode. Do you want to start in Safe Mode?” You might also see an event in the Event Viewer, as listed in the article linked below.
Affected platforms:
  • Client: Windows 10, version 2004; Windows 10, version 1909; Windows 10, version 1903; Windows 10, version 1809; Windows 10 Enterprise LTSC 2019; Windows 10, version 1803; Windows 10, version 1709; Windows 10, version 1607; Windows 10 Enterprise 2015 LTSB; Windows 8.1; Windows 7 SP1
Workaround: As an alternative, on your Windows 10 device you can use the Office365 on the web (OWA), also known as webmail. Outlook mobile is also unaffected. There is no workaround for this issue for the Outlook app on Windows 10 until the resolution is deployed to your device. We do not recommend using the command to revert to an earlier version.
Resolution: This Outlook issue has been resolved and will be deployed automatically to your device. This issue was not related to any update for Windows and no update for Windows is needed. We expect this issue to be completely resolved for all affected users by July 15, 2020 at 3:30 PM PST (10:30 PM UTC). You may also need to attempt to open Outlook a few times before it will be fully refreshed and open as expected. For more information, please see the support article, Active Investigation into Outlook Crashing on Launch and this twitter thread.