python向多个邮箱发邮件--注意接收是垃圾邮件

群发邮件注意：三处标红的地方

# -*- coding: UTF-8 -*-

import smtplib

from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
from email.header import Header
from email.mime.image import MIMEImage

# 第三方 SMTP 服务
mail_host="smtp.qq.com"  #设置服务器
mail_user="xxx@qq.com"    #用户名
mail_pass="xxxxxx"   #口令

sender = 'xxx@qq.com'
receivers = ['123@qq.com','456@qq.com','789@qq.com','987@qq.com','546@qq.com','321@qq.com']  # 接收邮件，可设置为你的QQ邮箱或者其他邮箱

msgRoot = MIMEMultipart('related')
msgRoot['From'] = Header("发送人", 'utf-8')
msgRoot['To'] =  ','.join(receivers)#注意
subject = '主题'
msgRoot['Subject'] = Header(subject, 'utf-8')

msgAlternative = MIMEMultipart('alternative')
msgRoot.attach(msgAlternative)

mail_msg = """
发送信息内容
"""
msgAlternative.attach(MIMEText(mail_msg, 'html', 'utf-8'))

try:
    smtpObj = smtplib.SMTP_SSL(mail_host, 465)
    smtpObj.login(mail_user,mail_pass)
    smtpObj.sendmail(sender, receivers, msgRoot.as_string())
    print "邮件发送成功"
except smtplib.SMTPException:
    print "Error: 无法发送邮件"