下面是一个使用Angular和Express.js的示例应用程序，通过前端表单发送电子邮件：

1. 前端Angular应用程序代码：

// app.component.ts

import { Component } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Component({
  selector: 'app-root',
  template: `
    
Send Email

    

      
      
      Send
    
  `,
})
export class AppComponent {
  email: string;
  message: string;

  constructor(private http: HttpClient) {}

  sendEmail() {
    const data = {
      email: this.email,
      message: this.message
    };

    this.http.post('/send-email', data).subscribe(() => {
      console.log('Email sent');
    });
  }
}

2. Express.js服务器端代码：

// server.js

const express = require('express');
const nodemailer = require('nodemailer');

const app = express();
app.use(express.json());

app.post('/send-email', (req, res) => {
  const { email, message } = req.body;

  const transporter = nodemailer.createTransport({
    service: 'gmail',
    auth: {
      user: 'your-email@gmail.com',
      pass: 'your-password'
    }
  });

  const mailOptions = {
    from: 'your-email@gmail.com',
    to: email,
    subject: 'Test Email',
    text: message
  };

  transporter.sendMail(mailOptions, (error, info) => {
    if (error) {
      console.error(error);
    } else {
      console.log('Email sent: ' + info.response);
      res.sendStatus(200);
    }
  });
});

app.listen(3000, () => {
  console.log('Server started on port 3000');
});

请确保已安装以下依赖项：

• Angular依赖项：@angular/core, @angular/common, @angular/forms, @angular/common/http
• Express.js依赖项：express, nodemailer

要运行应用程序，您需要在终端中分别运行Angular应用程序和Express.js服务器。