Outlook can't open a mailbox by using MAPI over HTTP
Original KB number: 3191500
Symptoms
Users can't open their mailboxes in Microsoft Outlook by using MAPI over HTTP.
Cause
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'
Resolution
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.