I upgraded Outlook on my office computer from 2010 to 2013, and then the ppt file I sent as an attachment could not be opened on my own computer. It said it was damaged and asked for repair, but the repair was ineffective. The file was also damaged when I saved it. The email received by others was fine. I sent it There is no problem with excel, only the pptx file is damaged. I searched online and found the solution as follows. The cause of the file damage is unknown: