Create the following registry key in order to force Outlook to use the newer authentication method for web services, such as EWS and Autodiscover.

  1. Exit Outlook.
  2. Start Registry Editor. To do this, use one of the following procedures, as appropriate for your version of Windows:
    • Windows 10, Windows 8.1 and Windows 8: Press Windows Key + R to open a Run dialog box. Type regedit.exe, and then press Enter.
    • Windows 7: Click Start, type regedit.exe in the search box, and then press Enter.
  3. In Registry Editor, locate and then click the following registry subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Exchange
  4. On the Edit menu, point to New, and then click DWORD Value.
  5. Type AlwaysUseMSOAuthForAutoDiscover, and then press Enter.
  6. Right-click AlwaysUseMSOAuthForAutoDiscover, and then click Modify.
  7. In the Value data box, type 1, and then click OK.
  8. Exit Registry Editor.