Trouble installing SMTP on Server 2012 Standard Core

I asked this on the windows 2012 forum, where I was advised to ask this on this form.

I have a Server core instance I am administrating via PowerShell remoting. It has IIS and Sql 2008R2 functioning correctly and I want to add SMTP. I've verified its running 2012 standard edition:

PS C:\Users\JDearing\Documents> CimInstance Win32_OperatingSystem|select caption

caption
-------
Microsoft Windows Server 2012 Standard

I try to install SMTP with the following command: 

Add-WindowsFeature SMTP-Server,RSAT-SMTP -source:wim:d:\sources\install.wim:1 -Debug -Verbose

It fails with:

Add-WindowsFeature : The request to add or remove features on the specified server failed.
Installation of one or more roles, role services, or features failed.
The source files could not be downloaded.
Use the "source" option to specify the location of the files that are required to restore the feature. For more information on specifying a source location, see
http://go.microsoft.com/fwlink/?LinkId=243077. Error: 0x800f0906+ CategoryInfo          : InvalidOperation: (@{Vhd=; Credent...Name=localhost}:PSObject) [Install-WindowsFeature], Exception+ FullyQualifiedErrorId : DISMAPI_Error__Cbs_Download_Failure,Microsoft.Windows.ServerManager.Commands.AddWindowsFeatureCommand
DEBUG: Call to GetAlterationRequestState provider method failed with error(s): The request to add or remove features on the specified server failed.
Installation of one or more roles, role services, or features failed.
The source files could not be downloaded.
Use the "source" option to specify the location of the files that are required to restore the feature. For more information on specifying a source location, see
http://go.microsoft.com/fwlink/?LinkId=243077. Error: 0x800f0906

The ISO is mounted to the D: drive and the image for 2012 standard server cor is indeed 1:

 PS C:\Users\JDearing\Documents> Get-windowsimage –imagepath d:\sources\install.wim


Index       : 1
Name        : Windows Server 2012 SERVERSTANDARDCORE
Description : Windows Server 2012 SERVERSTANDARDCORE
Size        : 7,178,226,690 bytes

Index       : 2
Name        : Windows Server 2012 SERVERSTANDARD
Description : Windows Server 2012 SERVERSTANDARD
Size        : 11,999,889,351 bytes

Index       : 3
Name        : Windows Server 2012 SERVERDATACENTERCORE
Description : Windows Server 2012 SERVERDATACENTERCORE
Size        : 7,172,264,095 bytes

Index       : 4
Name        : Windows Server 2012 SERVERDATACENTER
Description : Windows Server 2012 SERVERDATACENTER
Size        : 11,995,265,169 bytes