运行Bulk-Mailer项目 账密正确仍报smtplib.SMTPAuthenticationError

运行Bulk-Mailer项目的Main.py脚本批量发信时，触发SMTP鉴权报错：smtplib.SMTPAuthenticationError: (535, b'5.7.8 Username and Password not accepted')，确认账号登录密码填写正确仍无法解决。
原项目核心代码（已隐去隐私信息）如下：

import smtplib
import imghdr
import os
import pandas as pd
from email.message import EmailMessage

# your account credentials
maildid = "EMAIL"  # enter your email id here
password = "PASSWORD"  # enter your password here

files = []

# path of the folder which will be attached
path = "attachments"
attachments = os.listdir(path)

# creating a new list to store files along with path
for file in range(len(attachments)):
    files.append(f'{path}/{attachments[file]}')

# reading mail id's from excel sheet
cont = pd.read_excel("contacts.xlsx")
contacts = cont['mail id'].values  # storing all the mail id's in contacts list

for contact in contacts:
    message = EmailMessage()
    message['From'] = maildid
    message['To'] = contact
    message['Subject'] = 'Enter the Subject here'  # replace the subject

    """
    Note: if you want to send mail with content then use option 1 and delete the option 2
          or
          if you want to send HTML mail then use option 2 and delete option 1
    """

    # option 1
    message.set_content(
        'Enter the content here ')  # this is optional. if you are using web mails then this is not necessary.

    # option 2
    message.add_alternative("""\    
        <!DOCTYPPE html>
            <html>
                <body>

                    //Insert you html code here

                </body>
            </html>            
                            """, subtype='html')

    # attaching files to the mail
    for file in files:
        with open(file, 'rb') as f:
            file_data = f.read()
            file_type = imghdr.what(f.name)
            file_name = f.name
        message.add_attachment(file_data, maintype='application', subtype='octect-stream', filename=file_name)

    # Sending mails
    with smtplib.SMTP_SSL('smtp.gmail.com', 465) as smtp:
        smtp.login(maildid, password)
        smtp.send_message(message)

        # if the mail is Successfully sent then this statement will be printed
        print("Mail sent Successfully to {}".format(contact))

print("\nSuccessfully sent!!!")

• Gmail在2022年5月后正式下线了「低安全性应用访问」功能，直接使用账号登录密码走SMTP协议鉴权的方式已经被官方完全禁止，和密码输入正确与否没有关系。
• 原代码存在3处会影响正常运行的拼写/逻辑问题：
  • HTML文档声明多打了一个字母P，写为<!DOCTYPPE html>，会导致部分邮箱客户端无法正常识别HTML格式邮件
  • 附件MIME类型拼写错误，写为octect-stream，正确值为octet-stream，会导致附件无法被正常识别
  • 每发送一封邮件就重新建立一次SMTP连接，极易触发Gmail的发信限流规则，导致发送中途被拦截

• 先给用来发信的Gmail账号开启两步验证，这是生成应用专用密码的前置条件，未开启两步验证的账号不会显示应用密码生成入口。
• 在Gmail账号的安全设置页生成应用专用密码，应用类型选择「邮件」，设备选择当前运行脚本的设备即可，将生成的16位应用密码妥善保存。
• 将代码中password字段原本填写的Gmail账号登录密码，替换为刚才生成的16位应用专用密码，maildid字段仍填写完整的Gmail邮箱地址即可。
• 修正代码中的拼写错误，同时把SMTP连接初始化逻辑移到收件人遍历循环的外侧，复用同一个连接发送所有邮件，避免触发限流。

修正后的核心代码片段参考：

# 账号配置
maildid = "你的完整Gmail邮箱地址"
password = "你生成的16位应用专用密码" # 不要填账号日常登录的密码

# ... 省略附件加载、联系人读取的原有逻辑 ...

# SMTP连接移到循环外，只登录一次
with smtplib.SMTP_SSL('smtp.gmail.com', 465) as smtp:
    smtp.login(maildid, password)
    for contact in contacts:
        message = EmailMessage()
        message['From'] = maildid
        message['To'] = contact
        message['Subject'] = '你的邮件主题'

        # 纯文本内容配置
        message.set_content('你的纯文本邮件内容')

        # HTML内容配置，修正DOCTYPE拼写错误
        message.add_alternative("""\    
        <!DOCTYPE html>
            <html>
                <body>
                    <!-- 你的HTML邮件代码写在这里 -->
                </body>
            </html>            
                            """, subtype='html')

        # 添加附件，修正MIME类型拼写
        for file in files:
            with open(file, 'rb') as f:
                file_data = f.read()
                file_type = imghdr.what(f.name)
                file_name = f.name
            message.add_attachment(file_data, maintype='application', subtype='octet-stream', filename=file_name)
        
        smtp.send_message(message)
        print("Mail sent Successfully to {}".format(contact))

print("\nSuccessfully sent!!!")

内容的提问来源于stack exchange，提问作者Andy Thompson