send rich text email with python

mail.py

import smtplib
from email.mime.text import MIMEText
from email.header import Header

def mail(htm):
    sender = 'sender@163.com'
    receiver = 'receiver@163.com'
    subject = 'test'
    smtpserver = 'smtp.163.com'
    username = 'sender@163.com'
    password = 'password'
    msg = MIMEText(htm, 'html', 'utf-8')
    msg['Subject'] = Header(subject, 'UTF-8')
    msg['From'] = sender
    msg['To'] = receiver
    smtp = smtplib.SMTP()
    smtp.connect(smtpserver)
    smtp.login(username, password)
    smtp.sendmail(sender, receiver, msg.as_string())
    smtp.quit()