I'm kind of concerned about this. I didn't know about the whole signature requirement when I made the LOR request for a couple of my professors via interfolio, so I am not sure whether or not I clicked on the box for "This letter needs to be signed" or whatever when the request was sent? Is there anyway to verify if my letters are signed? I saw a couple threads on SDN that said interfolio will tell you if a letter is not signed, but I'm not sure if they still do this. If I call tomorrow, will interfolio tell me if my letters are signed?