在Python中发送邮件，不依赖其他第三方库

send_mail.py

# -*- coding: utf-8 -*-
"""
File Name   : send_mail.py
Create Date : 2020/10/24 15:26
"""
import threading
import smtplib
from email.mime.text import MIMEText

class SendMail:
    """ 封装发送邮件 """
    _instance = None
    def __new__(cls, *args, **kwargs):
        if cls._instance is None:
            cls._instance = object.__new__(cls)
        return cls._instance

    def __init__(self, smtpsever: str, sender: str, sender_pwd: str, to_email: str):
        """ 初始化
        :param smtpsever: smtp服务器地址，比如163的为smtp.163.com
        :param sender: 发信者的邮箱地址
        :param sender_pwd: 发信者的邮箱密码（授权码）
        :param to_email: 收信者邮箱地址
        """
        self.smtpsever = smtpsever
        self.sender = sender
        self.sender_pwd = sender_pwd
        self.to_email = to_email

        self._smtp = None  # type: smtplib.SMTP

    def login(self) -> smtplib.SMTP:
        """ 登录发信者 """
        smtp = smtplib.SMTP()
        smtp.connect(self.smtpsever)
        smtp.login(self.sender, self.sender_pwd)
        self._smtp = smtp
        print('login')
        return smtp

    def send(self, title: str, text: str, to_mail: str=None, _try_again_login: bool=True) -> bool:
        """ 发送邮件
        :param title: 邮件标题
        :param text: 邮件内容
        :param to_mail: 发送给谁，可选的，如果为None，那么将发送给初始化时定义的收信者
        :param _try_again_login: 由于放置时间过长登录状态会掉，是否进行重新登录
        :return:
        """
        if self._smtp is None:
            self.login()
        msg = MIMEText(text, 'html', 'utf-8')
        msg['from'] = self.sender
        msg['to'] = to_mail or self.to_email
        msg['subject'] = title
        try:
            self._smtp.sendmail(
                from_addr=self.sender,
                to_addrs=to_mail or self.to_email,
                msg=msg.as_string()
            )
            return True
        except Exception as e:
            if _try_again_login:
                self.login()
                return self.send(title=title, text=text, to_mail=to_mail, _try_again_login=False)
            return False

    def send_in_thread(self, title: str, text: str, to_mail: str=None):
        """ 在新线程中发送邮件，不阻塞当前操作 """
        threading.Thread(
            target=self.send,
            args=[title, text, to_mail]
        ).start()


if __name__ == '__main__':
    s = SendMail(smtpsever='smtp.163.com', sender='发件人@163.com', sender_pwd='发件人密码/授权码', to_email='收件人@qq.com')
    s.send_in_thread('title', 'text', to_mail='收件人@126.com')