EWS: Create message with PrivateDL recipient

Hello,
i noticed that Outlook allows sending mails to local contact groups (private distribution lists, PrivateDL).
When saving such a message as draft, it shows the recipient like this:

 <t:ToRecipients>
    <t:Mailbox>
       <t:Name>Test Distribution List</t:Name>
       <t:RoutingType>MAPIPDL</t:RoutingType>
       <t:MailboxType>PrivateDL</t:MailboxType>
       <t:ItemId Id="AAMkAGM2NTEyNGNlLTQ1YmEtNDc3MS1hYTcwLTU1OTUyNmYwMjc0OABGAAAAAABffnvz5cFJRKGuteRiOEEEBwDOHTPVqtslRIYX+WVhzyFIAAAAAAEOAADOHTPVqtslRIYX+WVhzyFIAADrHwPbAAA=" ChangeKey="EgAAAA=="/>
    </t:Mailbox>
 </t:ToRecipients>

However, when i try to use this mailbox as a recipient in CreateItem, the server replies with ErrorItemNotFound: The specified object was not found in the store., The store ID provided isn't an ID of an item.

Is it not possible to create a message with a PrivateDL as recipient using EWS?