Solution - Outlook Modern Authentication Registry Settings The solution listed below is the only one that resolved the problem for the people who are experiencing it. Additionally, some versions of office still contain an outdated Registry Key that forces modern Auth to be OFF. This is because Microsoft has made modern Auth mandatory and deprecated basic Auth. When they launch outlook, they are greeted by 'connecting to: and a password request from windows security. One, in particular, is having some issues using Outlook with Office 365. Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.I have discovered that many users can not sign into their outlook app. If you have extra questions about this answer, please click 'Comment'. If the answer is helpful, please click 'Accept Answer' and kindly upvote it.

Please refer to the Repair Office from the Control Panel part of this article. If that doesn't help, using Online Repair to repair Office from the Control Panel. Go to Control Panel > Mail > Show Profiles > Add, then re-add your account. I have noticed that you have configured your O365 account and Exchange account into one profile, please try to create a profile for each account and test if the issue continues:

What detailed version of Outlook are you using? Please make sure that you have upgraded it to the latest version (File > Office Account Update Now).Please refer to this article: How to perform a clean boot in Windows. If the issue only occurs with this computer, to check if the issue is caused by any other program on your computer, reboot your computer with clean boot. Does the issue only exist on this specific device? Can this problem be reproduced in other clients?.In order to better understand your problem, could you provide some detailed information: Please understand that in order to protect your privacy, I have hidden personal information.

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