python发送附件到kindle电子书接收不到

def send_attachment_kd(filename,toName,fromName,username,password):

    msg = MIMEMultipart()

    msg['Subject'] = 'convert'

    msg['From'] = "username"+"<"+fromName+">"

    msg['To'] = toName

    part = MIMEBase('application', "octet-stream")

    #fpath=os.path.join(KINDLE_DIR,filename)

    filename_txt=filename+".txt"

    #print filename_txt.decode('utf-8'

    filecOntent=open(filename_txt.decode('utf-8'),'r').read()

    part.set_payload(filecontent)

    Encoders.encode_base64(part)

    part.add_header('Content-Disposition', 'attachment; filename="Book.txt"')

    msg.attach(part)

    try:

        server=smtplib.SMTP()

        server.connect('smtp.qq.com')

        server.login(username,password)

        server.sendmail(msg['From'],toName,msg.as_string())

        server.quit()

        print "Send successfully"

    except Exception,e:

        print "Error"

        print str(e)