Error when overlay SharePoint calender with Exchange "The HTTP request is unauthorized with client authentication scheme 'Ntlm'. The authentication

Question

I am working on a SharePoint online team site collection inside Office 365. now i added a sharepoint calendar, then i chose to overlay it with exchnage as follow:-

where i defined the following values:-

• Outlokk web access URL = https://mail.****.com/owa/
• Exchnage web service URL = https://mail.****.com/ews/exchange.asmx

but when i access the sharepoint calender i got this error:-

The HTTP request is unauthorized with client authentication scheme 'Ntlm'. The authentication header received from the server was 'Negotiate,NTLM'. (e8855c9e-6056-5000-892f-f2f4a5b97961)

as follow:-

so can anyone advice on this error?

Answer 1

I can reproduce your issue.

This issue occurs because the ability to use the calendar overlay in a SharePoint Online or SharePoint Server calendar that is retrieved from Exchange Online isn't supported.

Refer to: https://support.microsoft.com/en-us/help/2997170/the-http-request-is-unauthorized-error-in-a-sharepoint-calendar