How to fix continue "Password Required" popup?

Recently, I have started facing issues with em client in which I keep getting a “Password Required” popup multiple times every day. If I enter the password and click OKAY I still get the popup few minutes later. If I click OKAY or CANCEL continuously 5 to 8 times, the pop will not appear for some time. But the problem is ongoing. I have two Microsoft 365 exchange email account setup and both have the same issue. I have already tried to update Em Client to the latest version and I have tried to delete the email account and re-add it but the problem is still there.

This is because O365 servers no longer accept username/password logins.

Please see: Microsoft disables Basic authentication for all accounts | eM Client

The account is already setup using Automatic setup. " that means the password is checked directly with Microsoft server which then issues an access token to eM Client."

But I am still facing this issue.

That means the account is not setup with modern authentication. It will not work because the server no longer accepts username/password logins.

Please try the setup again. Go to Menu > Accounts and remove the account. Then add it again by clicking on Add Account. Enter the email address in the automatic setup. You will be passed to your web browser after a few questions, and that is where you enter the authentication details. Then you will be passed back to eM Client where the account will have been setup with modern authentication. You will not be prompted for a username/password again as it doesn’t use them.

Yes, I have already done this and I am still facing the same problem.

Probably the other account then.