Send email in workflow will not select Outlook form

I am using Dynamics CRM 2011 on-premise with CRM for Outlook clients. I selected  the standard Outlook form for use with my emails because it supports signatures and graphics. Adding an email activity to a Lead or Cotact works fine with this form. However, when I try to send an email using a Workflow, the workflow selects the CRM Form not the Outlook one, How can I get the workflow to use the Outlook form?