Sender has Outlook 2010/Exchange 2007. Recipient has GroupWise. Sender is emailing some PDSs and recipient gets them as TNEF.001. This only happens to one particular person in the receiving organization. Anyone else in the Sending organization can send to that recipient just fine. Doesn't matter if the email is in HTML, Rich Text or plain text. Outlook is set to send as HTML. Recipient is in Sender's contacts at an HTML formatted address.