For many users around the world, Outlook for Windows client is crashing immediately after starting up. Microsoft is aware of this issue and currently investigating to find the cause. The latest update could be the cause of this issue. Meanwhile, users can access their mail through Outlook.com and Outlook mobile apps.
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.
If you really need to use Outlook for Windows client, you can revert back to the previous version of Outlook using the following method.
C:Program FilesCommon Filesmicrosoft sharedClickToRunOfficeC2RClient.exe” /update user updatetoversion=16.0.12827.20470
Office 2016: “C:Program FilesCommon Filesmicrosoft sharedClickToRunOfficeC2RClient.exe” /update user updatetoversion=16.0.12827.20470
Source: Microsoft