Go语言使用net/smtp发送电子邮件完整示例

type configInfo struct {
	smtpAddr string
	smtpPort string
	secret   string // 通常为授权码而非登录密码
}

type emailContent struct {
	fromAddr    string
	contentType string // "html" 或 "plain"
	theme       string
	message     string
	toAddr      []string
}

func sendEmail(c *configInfo, e *emailContent) error {
	// 1. 拼接服务器地址
	smtpAddr := c.smtpAddr + ":" + c.smtpPort
	
	// 2. 创建认证对象
	auth := smtp.PlainAuth("", e.fromAddr, c.secret, c.smtpAddr)
	
	// 3. 确定内容类型头
	var contentTypeHeader string
	if e.contentType == "html" {
		contentTypeHeader = "Content-Type: text/html; charset=UTF-8"
	} else {
		contentTypeHeader = "Content-Type: text/plain; charset=UTF-8"
	}
	
	// 4. 循环发送给每个收件人
	for _, to := range e.toAddr {
		// 严格按照 RFC 822 格式构建 msg
		msg := "To: " + to + "\r\n" +
			"From: " + e.fromAddr + "\r\n" +
			"Subject: " + e.theme + "\r\n" +
			contentTypeHeader + "\r\n" +
			"\r\n" +
			e.message // 此处可直接填入HTML片段
		
		err := smtp.SendMail(smtpAddr, auth, e.fromAddr, []string{to}, []byte(msg))
		if err != nil {
			return err
		}
	}
	return nil
}

func main() {
	config := configInfo{
		smtpAddr: "smtp.yeah.net",
		smtpPort: "25",
		secret:   "your_authorization_code",
	}
	
	content := emailContent{
		fromAddr:    "sender@yeah.net",
		toAddr:      []string{"recipient@qq.com", "other@126.com"},
		contentType: "html",
		theme:       "测试邮件主题",
		message:     "<h1>Hello</h1><p>这是一封通过Go发送的HTML邮件</p>",
	}
	
	if err := sendEmail(&config, &content); err != nil {
		log.Fatal(err)
	}
	fmt.Println("发送成功")
}