A prof of mine who i feel probably wrote me a great letter of rec, wrote one right before she had an unexpected medical emergency and took off the rest of the semester, she had submitted it to interfolio before she took off and notified me. When i asked interfolio to check all my letters for letterhead and signatures, they all had signatures, hers contained no letterhead. Right now she is MIA (and really i don't want to bug her until i know she is recovered, so far no one has really heard from her). My question is, if the time rolls around for me to submit my letters, should i use hers? or should i try and get another letter from another prof that doesn't know me as well... i figured that although letter head is nice because it is official but at least there still is a signature... if they really questioned the validity of the letter they could jus contact the university. What does everyone else think about possibly using a letter that isn't on letterhead? Maybe i can explain the situation? Are letterhead for letters of rec absolutely necessary for submission? any Adcom members opinion/advice would be greatly appreciated too.