利用smtplib写邮件出现 Error: 无法发送邮件SMTP AUTH extension not supported by server

1、出现问题的源代码

# -*- coding: UTF-8 -*-
import smtplib
from email.mime.text import MIMEText
from email.header import Header

# 第三方 SMTP 服务
mail_host = "***"  # 设置服务器
mail_user = "**"  # 用户名


sender = '**'
receivers = ['***]  # 接收邮件，可设置为你的QQ邮箱或者其他邮箱

message = MIMEText('Python 邮件发送测试...', 'plain', 'utf-8')
message['From'] = Header("菜鸟教程", 'utf-8')
message['To'] = Header("测试", 'utf-8')

subject = 'Python SMTP 邮件测试'
message['Subject'] = Header(subject, 'utf-8')
# print (message.as_string())
try:
    smtpObj = smtplib.SMTP()
    # smtpObj.set_debuglevel(2)
    smtpObj.connect(mail_host, 25)  # 25 为 SMTP 端口号
    mail_pass = input("请输入邮箱密码:") # 口令
    # smtpObj.starttls()
    smtpObj.login(mail_user, mail_pass)
    smtpObj.sendmail(sender, receivers, message.as_string())
    print("邮件发送成功")
except Exception as e:
    print("Error: 无法发送邮件%s"%e)

2、总是提示SMTP AUTH extension not supported by server

解决办法：

smtpObj.starttls()