Office desktop client users can face this issue due to several possible reasons when the outlook prompts for credentials frequently and it can be frustrating at times.

  1. When you open outlook and see need password prompt on the lower right corner.
  2. Close all office applications currently running on your desktop.
  3. Now go to Control panel > Credentials Manager > Windows Credentials
  4. Go to generic credentials tab and remove all the MicrosoftOffice16_Data
  5. Click on drop down arrow and then click Remove.

  6. You will get a prompt that if your " Are sure you want to permanently delete this Generic credentials ? ".Click on Yes. Do this for all MicrosoftOffice2016_Data.

  7. Now Open any of the office applications like Word or Excel and sign in to office application using your Work credentials.

  8. Enter your work/school email and credentials.
  9. Now open Outlook, you'll again get a prompt to enter your credentials and enter the credentials and do not forget to tick the checkmark "Remember my credentials" and click Ok

  10. Outlook gets connected to Microsoft Exchange and you no longer get the prompt to enter the credentials again.

    Note: Taking Office 2016(Windows10) as reference, similar steps can be followed for other Office versions on different operating systems to stop this issue. This solves problem 9 out of 10 times but if this does not solve the problem then other troubleshooting steps needs to be performed.