Are the attachments that you are receiving failing to download or not opening? IS this causing you trouble to commence your day to day work? You can ask the sender to resend the file by either changing its name or location. Also, make sure that there are no punctuation marks used when you name the file. And if even after that the documents are not opening, then you can ask the sender to either copy paste the content or you can talk to the adepts at Optimum email customer care number and employ the basic troubleshooting methods as per their suggestion.