Outlook can't open a mailbox by using MAPI over HTTP

Original KB number:   3191500


Users can't open their mailboxes in Microsoft Outlook by using MAPI over HTTP.


This issue occurs if all authentication methods for the MAPI virtual directory are disabled.

Editing the MAPI virtual directory through the Exchange Admin Center causes the Set-MapiVirtualDirectory cmdlet to run without having IISAuthenticationMethods configured. The syntax of the cmdlet resembles the following:

Set-MapiVirtualDirectory -ExternalUrl 'https://mapi.contoso.com/mapi' -IISAuthenticationMethods @() -Identity '1d4e91f5-b1ae-4863-a071-2822210f05b9'


To resolve this issue, use the Set-MapiVirtualDirectory cmdlet to enable the IIS authentication methods, as follows:

Get-MapiVirtualDirectory -Server <ServerName>| Set-MapiVirtualDirectory -IISAuthenticationMethods Ntlm,OAuth,Negotiate

More information

For more information about this cmdlet, see Set-MapiVirtualDirectory.