as shown in the figure, after receiving the email, the attachment title is not set by me, and the suffix name is changed to xls 
 
 
Code snippet:
file = MIMEText(open(filepath,"rb").read(),"xls","gb2312")
        file["Content-Type"] = "application/octet-stream"
        file["Content-Disposition"] = "attachment;filename=%s" % filename
        -sharp
        file.add_header("Content-1","%s" % filename)
        msg.attach(file)
also tested that the MIMEBase, result is the same.
