python3 发送邮件到126邮箱失败，提示 TimeoutError: [WinError_编程技术网-程序员技术内容聚合平台

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我用下面代码试图发送邮件到126邮箱失败，请问是什么原因

import smtplib
from email import encoders 
from email.header import Header 
from email.mime.text import MIMEText 
from email.utils import parseaddr 
from email.utils import formataddr 

def format_addr(s):
    name, addr = parseaddr(s)
    return formataddr((Header(name, "utf-8").encode(), addr))

from_email = "xxxxx@126.com"
from_email_pwd = "xxxxxxx"
to_email = "xxxxx@126.com"
smtp_server = "smtp.126.com"

msg = MIMEText("<html><body><h3>hello</h3><p>hello, send by python</p></body></html>", "html", "utf-8")
msg["From"] = format_addr("%s" %(from_email))
msg["To"] = format_addr("%s" %(to_email))
msg["Subject"] = Header("python email", "utf-8").encode()

server = smtplib.SMTP(smtp_server, 25)
server.set_debuglevel(1)
server.login(from_email, from_email_pwd)
server.sendmail(from_email, [to_email], msg.as_string())
server.quit()

提示错误：

TimeoutError: [WinError 10060] A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond