使用Python的smtplib可以发送QQ邮件，代码如下

#!/usr/bin/python3
import smtplib
from email.mime.text import MIMEText
from email.header import Header


sender = '111@qq.com'  # 发送邮箱
receivers = ['222@qq.com']  # 接收邮箱
auth_code = "abc"  # 授权码

message = MIMEText('Python发送邮件', 'plain', 'utf-8')
message['From'] = Header("Sender<%s>" % sender)  # 发送者
message['To'] = Header("Receiver<%s>" % receivers[0])  # 接收者

subject = 'Python SMTP 邮件测试'
message['Subject'] = Header(subject, 'utf-8')


try:
    server = smtplib.SMTP_SSL('smtp.qq.com', 465)
    server.login(sender, auth_code)
    server.sendmail(sender, receivers, message.as_string())
    print("邮件发送成功")
    server.close()
except smtplib.SMTPException:
    print("Error: 无法发送邮件")

发送邮件服务器要用465端口，否则如下错误：
login的密码不是邮箱登录密码，而是授权码，需要在QQ邮箱设置-账号里获取。

否则会报如下错误：

SMTPServerDisconnected: Connection unexpectedly closed

SSLError: [SSL: WRONG_VERSION_NUMBER] wrong version number (_ssl.c:1002)

发送消息的From和To要用标准格式，否则报错：

SMTPDataError: (550, b'The "From" header is missing or invalid. Please follow RFC5322, RFC2047, RFC822 standard protocol. https://service.mail.qq.com/detail/124/995.')

参考

https://wx.mail.qq.com/list/readtemplate?name=app_intro.html#/agreement/authorizationCode
https://help.mail.qq.com/detail/0/994
https://docs.python.org/zh-cn/3/library/netdata.html
https://docs.python.org/zh-cn/3/library/smtplib.html