I agree with the post above. I've sent several LOCIs to my waitlisted schools and have received replies saying, "Thank you. This will be added to your file," as well as, "We no longer open attachments due to threat of virus. Please send this as the text in an email or mail the document to our admissions office." I would call and ask. It appears that sending it as the text of an email is sufficient to even those who do not open the attachments. However, you may not be able to beautify the document through format and headings. HTH.