You will have to go into the Microsoft Exchange settings and security to fix this:

 

  1. Launch the Control Panel. In Windows 7, 8 & 10 you can just type Control Panel into the Start Menu and select it from the results.
  2. Find Mail and double click to open it.
  3. Click where it says Show Profiles, choose the Outlook profile you need to check (usually just your name), and then click Properties.




outlook 365 email acocunt properties




  1. Click Email Accounts to open Account Settings and within the E-mail tab, click Change.




change outlook email account settings office 365



  1. In the Change Account box, click More Settings.
  2. In the Microsoft Exchange window, navigate to the Security tab.



Set Microsoft Exchange security to anonymous authentication




  1. From the Login Network Security dropdown menu choose Anonymous Authentication and click Apply then OK.
  2. Now back in the Change Account window, click Next, then click Finish.