Celery异步发送注册邮件时出现DNS解析错误求助

更换电脑后，使用Celery实现的异步邮件注册功能触发请求时出现DNS解析错误，Celery控制台可正常识别任务，但执行时抛出如下异常：

Traceback (most recent call last):
  File "d:\python3\lib\site-packages\dns\resolver.py", line 982, in nameservers
    raise NotImplementedError
NotImplementedError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "d:\python3\lib\site-packages\celery\app\trace.py", line 451, in trace_task
    R = retval = fun(*args, **kwargs)
  File "d:\python3\lib\site-packages\celery\app\trace.py", line 734, in __protected_call__
    return self.run(*args, **kwargs)
  File "E:\Exploit_blog\blog_index_html\tasks.py", line 9, in send_email
    send_mail(
  File "d:\python3\lib\site-packages\django\core\mail\__init__.py", line 61, in send_mail
    return mail.send()
  File "d:\python3\lib\site-packages\django\core\mail\message.py", line 284, in send
    return self.get_connection(fail_silently).send_messages([self])
  File "d:\python3\lib\site-packages\django\core\mail\backends\smtp.py", line 102, in send_messages
    new_conn_created = self.open()
  File "d:\python3\lib\site-packages\django\core\mail\backends\smtp.py", line 62, in open
    self.connection = self.connection_class(self.host, self.port, **connection_params)
  File "d:\python3\lib\smtplib.py", line 1034, in __init__
    SMTP.__init__(self, host, port, local_hostname, timeout,
  File "d:\python3\lib\smtplib.py", line 253, in __init__
    (code, msg) = self.connect(host, port)
  File "d:\python3\lib\smtplib.py", line 339, in connect
    self.sock = self._get_socket(host, port, self.timeout)
  File "d:\python3\lib\smtplib.py", line 1040, in _get_socket
    new_socket = super()._get_socket(host, port, timeout)
  File "d:\python3\lib\smtplib.py", line 310, in _get_socket
    return socket.create_connection((host, port), timeout,
  File "d:\python3\lib\site-packages\eventlet\green\socket.py", line 44, in create_connection
    for res in getaddrinfo(host, port, 0, SOCK_STREAM):
  File "d:\python3\lib\site-packages\eventlet\support\greendns.py", line 543, in getaddrinfo
    qname, addrs = _getaddrinfo_lookup(host, family, flags)
  File "d:\python3\lib\site-packages\eventlet\support\greendns.py", line 505, in _getaddrinfo_lookup
    answer = resolve(host, qfamily, False, use_network=use_network)
  File "d:\python3\lib\site-packages\eventlet\support\greendns.py", line 450, in resolve
    return _proxy.query(name, rdtype, raise_on_no_answer=raises,
  File "d:\python3\lib\site-packages\eventlet\support\greendns.py", line 394, in query
    step(self._resolver.query, qname, rdtype, rdclass, tcp, source, raise_on_no_answer=False)
  File "d:\python3\lib\site-packages\eventlet\support\greendns.py", line 334, in _resolver
    self.clear()
  File "d:\python3\lib\site-packages\eventlet\support\greendns.py", line 342, in clear
    self._resolver = dns.resolver.Resolver(filename=self._filename)
  File "d:\python3\lib\site-packages\dns\resolver.py", line 756, in __init__
    self.read_registry()
  File "d:\python3\lib\site-packages\dns\resolver.py", line 858, in read_registry
    self.nameservers = info.nameservers
  File "d:\python3\lib\site-packages\dns\resolver.py", line 984, in nameservers
    raise ValueError(f'nameserver {nameserver} is not an '
ValueError: nameserver ; is not an IP address or valid https URL

任务代码 #

from django.core.mail import send_mail

from celery import shared_task


# 发送邮件验证码，使用task进行异步处理，获取从视图层获取来的值，然后发送到用户邮箱中
@shared_task
def send_email(request, rand_str):
    send_mail(
        subject='验证码',
        message='你的验证码为:' + rand_str + '请不要将你的验证码告诉其他人',
        from_email='TEXT',
        recipient_list=[request],
        fail_silently=False
    )
    return (request, rand_str)

Django邮件配置 #

EMAIL_BACKEND = 'django.core.mail.backends.smtp.EmailBackend'
EMAIL_USE_TLS = False 
EMAIL_USE_SSL = True  
EMAIL_HOST = 'smtp.gmail.com'  
EMAIL_PORT = 587
EMAIL_HOST_USER = 'xxx'  
EMAIL_HOST_PASSWORD = 'xxx' 

错误原因分析 #

核心报错ValueError: nameserver ; is not an IP address or valid https URL表明：系统在读取DNS服务器配置时，错误将分号;识别为DNS地址，导致无法解析SMTP服务器域名smtp.gmail.com。

更换电脑后出现该问题，根源在于新电脑的DNS配置存在格式错误：

• Windows系统的DNS注册表或网络配置中存在多余的分号符号
• Eventlet的greendns模块读取系统DNS配置时，误将分号解析为有效DNS服务器地址

此外，邮件配置中EMAIL_USE_SSL = True与EMAIL_PORT = 587不匹配，Gmail的SSL对应端口为465，TLS对应587，该配置可能加剧连接失败问题。

解决办法 #

1. 修复系统DNS配置 #

检查并修正Windows网络DNS设置：

• 打开「网络和共享中心」→ 更改适配器设置 → 右键当前网络连接 → 属性 → 双击「Internet协议版本4 (TCP/IPv4)」
• 确保DNS服务器地址为有效IP（如8.8.8.8、114.114.114.114），无多余符号（如分号）
• 若使用自动获取DNS，可临时切换为手动指定公共DNS测试

2. 强制指定DNS给Eventlet #

在Celery启动前，手动设置DNS服务器，避免读取系统错误配置：

import eventlet
eventlet.support.greendns.set_default_resolver('8.8.8.8')

3. 修正邮件加密方式与端口匹配 #

调整Gmail邮件配置，确保加密方式与端口对应：

# 方案1：使用TLS
EMAIL_USE_TLS = True
EMAIL_USE_SSL = False
EMAIL_PORT = 587

# 方案2：使用SSL
EMAIL_USE_TLS = False
EMAIL_USE_SSL = True
EMAIL_PORT = 465

4. 绕过Eventlet的DNS解析 #

若上述方法无效，禁用Eventlet的greendns，改用系统原生DNS解析：

import eventlet
eventlet.monkey_patch(dns=False)

内容的提问来源于stack exchange，提问作者Exploit