First, please post only once. Posting the same topic twice causes confusion and causes those wanting assist to try replying to one request while others may be attempting to assist on the other. On your issue, I encourage you to exit libreoffice prior to sending the spreadsheet. when you receive it back to yourself, I suggest renaming it. That is, my fear is that sending to yourself may cause the libreoffice software to be preventing YOU from editing it as a duplicate, an issue that may not affect your recipient. My concern may be incorrect, but there is the chance that you are doing all of this while keeping the spreadsheet open in libreoffice.