First of all, understand that I also went through trouble with this modern authentication that is turn on and causing you to see “Always prompt for logon credentials” option is grey out under Outlook application. You would like to have app password for your outlook application but got stop to proceed so because of modern authentication. Is also troublesome to have to keep on keying the code whenever you are re-login your Outlook application without the app password setup on your Outlook account.
*Modern authentication only supports 2013 or the earlier release, please refer to reference for further information
Example for Outlook 2016;
Where to see the grey out “Always prompt for logon credentials”?
File > Info > Account settings > Account Name and Sync Settings > Select More Settings > go to Security tab
However, to sign in with app password, there are 2 options;
- If you have an existing account in your Outlook application and have “Always prompt for a password to log in” is enabled then you will just have to key in the app password in the prompt panel.
- If you are re-adding or add new account then you will have to key in the app password during your setup of the account for your Outlook application.
*These options doesn’t just limit to Outlook application only
So to disable the modern authentication you may need to add-on a registry;
- Go to registry
- Locate this directory HKCU\SOFTWARE\Microsoft\Office\16.0\Common\Identity\EnableADAL
- If “EnableADAL” registry is not created yet then create it as DWORD and set the value to “0”
- If you have already has this registry then just change the value to “0”
- Close the registry and restart your Outlook application (by closing and re-open)
- You will see the prompt for the credential to log in is shown while you launch your Outlook application
- Key in your app password and select remember password
*Is much simple to add registry
*But I recommend that you remove the profile and then re-add