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

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.
Properties

Article ID: 3191500 - Last Review: Sep 28, 2016 - Revision: 1

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