It was just another morning at work on July 15, 2020, for many Windows users. They turned on their computers -- some of them may have noted that they'd gotten an Outlook program update -- and then they tried to open their e-mail in Outlook… Suddenly their day took a turn for the worst.
For many, Windows Outlook silently crashed when they tried to launch it. Many Office 365 business users also found that the Outlook mail service also launched only to immediately crash. Hours later, Microsoft admitted on Twitter there was a real problem.
We're investigating whether a recently deployed update could be the source of this issue. As a workaround, users can utilize Outlook on the web or their mobile clients. Additional details can be found in the admin center under EX218604 and OL218603.
Later, Microsoft tweeted it was "rolling out a fix for this issue, and we expect the mitigation to reach all customers over the next few hours."
This failure seems to have been the result of last night's Outlook update. These were meant to give Outlook, across all its different versions, all the same features. It failed.
According to suggestions on the Reddit Sysadmin forum, you can fix the problem on local PCs by rolling back to the monthly channel 20470 release. You do this with the following steps:
Go to the admin command prompt and:
cd "\Program Files\Common Files\microsoft shared\ClickToRun"
Then run, as the administrator,
officec2rclient.exe /update user updatetoversion=16.0.12827.20470
At this time, there is no known Microsoft Windows Installer (MSI) repair.
This is a stop-gap fix, but it's better than swearing at your computer. Once Microsoft has the problem fixed, which I expect in the short run, it will consist of rolling back the update. You'll want to use the official fix.
If you're using Outlook as a service, try, as Microsoft suggests, to use the Outlook web interface or a mobile app.