I am about to submit my RFE response to NSC. At the end of my RFE, it says "please use the enclosed envelope for mailing this evidence back to this office". But I didn't get any enclosed envelope at all. I read on USCIS website that "Evidence submitted without proper return mailing envelope will be difficult to match up with the pending case and may be treated as general correspondence. What should I do? How did you mail your RFE response? Thanks.