Flask接收表单数据后无法发送至Gmail邮箱问题求助

问题描述 #

已获取Google应用专用密码，单独测试邮件发送代码功能正常，用户名和密码无误，且能成功接收HTML表单提交的数据，但邮件始终无法送达目标Gmail邮箱。

相关代码 #

Flask邮件发送函数 #

def send_email(name, email, phone, message):
    smtp_server = 'smtp.gmail.com'
    smtp_port = 587
    smtp_username = 'sara@gmail.com'
    smtp_password = 'password'

    from_email = 'sara@gmail.com'
    to_email = 'sara@gmail.com'
    subject = 'Hello!'
    body = f'Name: {name}\nEmail: {email}\nPhone: {phone}\nMessage:{message}'
    message = f'Subject: {subject}\n\n{body}'

    with smtplib.SMTP(smtp_server, smtp_port) as smtp:
        smtp.starttls()
        smtp.login(smtp_username, smtp_password)
        smtp.sendmail(from_email, to_email, message)

contact.html模板代码 #

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no" />
        <meta name="description" content="" />
        <meta name="author" content="" />
        <title>Clean Blog - Start Bootstrap Theme</title>
        <link rel="icon" type="image/x-icon" href="{{ url_for('static',filename='assets/favicon.ico') }}" />
        <!-- Font Awesome icons (free version)-->
        <script src="https://use.fontawesome.com/releases/v5.15.4/js/all.js" crossorigin="anonymous"></script>
        <!-- Google fonts-->
        <link href="https://fonts.googleapis.com/css?family=Lora:400,700,400italic,700italic" rel="stylesheet" type="text/css" />
        <link href="https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,800italic,400,300,600,700,800" rel="stylesheet" type="text/css" />
        <!-- Core theme CSS (includes Bootstrap)-->
        <link href="{{ url_for('static', filename='css/styles.css') }}" rel="stylesheet" />
    </head>
    <body>
        {% include "header.html" %}

        <!-- Page Header-->
<header
  class="masthead"
  style="background-image: url('../static/assets/img/contact-bg.jpg')"
>
  <div class="container position-relative px-4 px-lg-5">
    <div class="row gx-4 gx-lg-5 justify-content-center">
      <div class="col-md-10 col-lg-8 col-xl-7">
        <div class="page-heading">
            {% if msg_sent %}
          <h1>Successfully sent your message</h1>
          {% else: %}
          <h1>Contact Me</h1>
          {% endif %}
          <span class="subheading">Have questions? I have answers.</span>
        </div>
      </div>
    </div>
  </div>
</header>
<!-- Main Content-->
<main class="mb-4">
  <div class="container px-4 px-lg-5">
    <div class="row gx-4 gx-lg-5 justify-content-center">
      <div class="col-md-10 col-lg-8 col-xl-7">
        <p>
          Want to get in touch? Fill out the form below to send me a message and
          I will get back to you as soon as possible!
        </p>
        <div class="my-5">
          <!-- * * * * * * * * * * * * * * *-->
          <!-- * * Simplified SB Contact Form for the Tutorial* *-->
          <!-- Solution: change url for the action to 'contact'-->
          <form
            id="contactForm"
            name="sentMessage"
            action="{{ url_for('contact') }}"
            method="post"
          >
            <div class="form-floating">
              <input
                class="form-control"
                id="name"
                name="name"
                type="text"
                placeholder="Enter your name..."
                required
              />
              <label for="name">Name</label>
            </div>
            <div class="form-floating">
              <input
                class="form-control"
                id="email"
                name="email"
                type="email"
                placeholder="Enter your email..."
                required
              />
              <label for="email">Email address</label>
            </div>
            <div class="form-floating">
              <input
                class="form-control"
                id="phone"
                name="phone"
                type="tel"
                placeholder="Enter your phone number..."
                required
              />
              <label for="phone">Phone Number</label>
            </div>
            <div class="form-floating">
              <textarea
                class="form-control"
                id="message"
                name="message"
                placeholder="Enter your message here..."
                required
                style="height: 12rem"
              ></textarea>
              <label for="message">Message</label>
            </div>
            <br />
            <button
              class="btn btn-primary text-uppercase"
              id="submitButton"
              type="submit"
            >
              Send
            </button>
          </form>
        </div>
      </div>
    </div>
  </div>
</main>
        {% include "footer.html" %}
        <!-- Bootstrap core JS-->
        <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/js/bootstrap.bundle.min.js"></script>
        
        <script src="{{ url_for('static',filename='js/scripts.js') }}"></script>

        <script src="https://cdn.startbootstrap.com/sb-forms-latest.js"></script>
    </body>
</html>

运行日志 #

127.0.0.1 - - [30/Jan/2024 23:34:01] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [30/Jan/2024 23:34:01] "GET /static/css/styles.css HTTP/1.1" 304 -
127.0.0.1 - - [30/Jan/2024 23:34:01] "GET /static/js/scripts.js HTTP/1.1" 304 -
127.0.0.1 - - [30/Jan/2024 23:34:01] "GET /static/assets/img/home-bg.jpg HTTP/1.1" 304 -
127.0.0.1 - - [30/Jan/2024 23:34:05] "GET /contact HTTP/1.1" 200 -
127.0.0.1 - - [30/Jan/2024 23:34:05] "GET /static/css/styles.css HTTP/1.1" 304 -
127.0.0.1 - - [30/Jan/2024 23:34:05] "GET /static/js/scripts.js HTTP/1.1" 304 -
127.0.0.1 - - [30/Jan/2024 23:34:05] "GET /static/assets/img/contact-bg.jpg HTTP/1.1" 304 -
127.0.0.1 - - [30/Jan/2024 23:34:11] "POST /contact HTTP/1.1" 200 -
Sara 
sara@gmail.com
03456789
cv
127.0.0.1 - - [30/Jan/2024 23:34:11] "GET /static/css/styles.css HTTP/1.1" 304 -
127.0.0.1 - - [30/Jan/2024 23:34:11] "GET /static/js/scripts.js HTTP/1.1" 304 -
127.0.0.1 - - [30/Jan/2024 23:34:11] "GET /static/assets/img/contact-bg.jpg HTTP/1.1" 304 -

排查与解决步骤 #

1. 确认send_email函数是否被调用 #

从日志可见表单数据已被打印，但无任何邮件发送相关日志，大概率是Flask的contact路由在处理POST请求时，没有调用send_email函数。检查你的路由代码，确保在获取表单数据后执行了send_email(name, email, phone, message)。

2. 添加错误捕获与日志输出 #

原代码无异常处理逻辑，即使邮件发送失败也不会输出错误信息，无法定位问题。修改send_email函数，添加SMTP异常捕获：

import smtplib
from smtplib import SMTPException

def send_email(name, email, phone, message):
    smtp_server = 'smtp.gmail.com'
    smtp_port = 587
    smtp_username = 'sara@gmail.com'
    smtp_password = 'password'  # 替换为你的应用专用密码

    from_email = 'sara@gmail.com'
    to_email = 'sara@gmail.com'
    subject = 'Hello!'
    body = f'Name: {name}\nEmail: {email}\nPhone: {phone}\nMessage:{message}'
    message = f'Subject: {subject}\n\n{body}'

    try:
        with smtplib.SMTP(smtp_server, smtp_port) as smtp:
            smtp.starttls()
            smtp.login(smtp_username, smtp_password)
            smtp.sendmail(from_email, to_email, message)
        print("邮件发送成功")
    except SMTPException as e:
        print(f"邮件发送失败: {str(e)}")

3. 检查垃圾邮件文件夹 #

Gmail可能会将自动发送的邮件标记为垃圾邮件，登录目标邮箱查看垃圾邮件目录，确认邮件是否被误判。

4. 使用标准邮件格式构建邮件 #

手动拼接的邮件格式可能不符合规范，被邮件服务商拒收。改用email模块构建MIME格式的邮件：

from email.mime.text import MIMEText
from email.header import Header
import smtplib
from smtplib import SMTPException

def send_email(name, email, phone, message):
    smtp_server = 'smtp.gmail.com'
    smtp_port = 587
    smtp_username = 'sara@gmail.com'
    smtp_password = 'password'

    from_email = 'sara@gmail.com'
    to_email = 'sara@gmail.com'
    subject = 'Hello!'
    body = f'Name: {name}\nEmail: {email}\nPhone: {phone}\nMessage:{message}'

    # 构建规范的MIME邮件
    msg = MIMEText(body, 'plain', 'utf-8')
    msg['From'] = Header(from_email, 'utf-8')
    msg['To'] = Header(to_email, 'utf-8')
    msg['Subject'] = Header(subject, 'utf-8')

    try:
        with smtplib.SMTP(smtp_server, smtp_port) as smtp:
            smtp.starttls()
            smtp.login(smtp_username, smtp_password)
            smtp.sendmail(from_email, to_email, msg.as_string())
        print("邮件发送成功")
    except SMTPException as e:
        print(f"邮件发送失败: {str(e)}")

内容的提问来源于stack exchange，提问作者luna28blue