I notices that when I write a email and have changed the contents of the email a few times before I send out. It is ok for the sender to see it with a mail client. It also show normal when I received reply from sender and view it with Thunderbird. However, it show that when I received the reply email back and it show all the contents I changed with difference emails in Android mails. I think it must be something to do with Thunderbird because it do not happen with other mail client.