golang编写代码发邮件

AI提示词
用go语言直接向mx记录的25端口发邮件，要采用STARTTLS连接方式，要包含Message-ID

package main

import (
    "crypto/tls"
    "fmt"
    "log"
    "math/rand"
    "net"
    "net/mail"
    "net/smtp"
    "strings"
    "time"
)

func main() {
    from := "[email protected]"
    to := "[email protected]"
    subject := "Test Email via STARTTLS"
    body := "This is a test email sent using STARTTLS."

    err := SendMail(from, to, subject, body)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println("Email sent successfully")
}

func generateMessageID(from string) string {
    timestamp := time.Now().UnixNano()
    randomPart := rand.Int()
    domain := strings.Split(from, "@")[1]
    return fmt.Sprintf("<%d.%d@%s>", timestamp, randomPart, domain)
}

func SendMail(from, to, subject, body string) error {
    // 1. 解析收件人域名的MX记录
    domain := strings.Split(to, "@")[1]
    mxRecords, err := net.LookupMX(domain)
    if err != nil {
        return fmt.Errorf("failed to lookup MX records: %v", err)
    }

    if len(mxRecords) == 0 {
        return fmt.Errorf("no MX records found for domain %s", domain)
    }

    // 2. 连接到第一个MX记录的25端口
    mxHost := mxRecords[0].Host
    conn, err := net.Dial("tcp", mxHost+":25")
    if err != nil {
        return fmt.Errorf("failed to connect to MX host %s: %v", mxHost, err)
    }
    defer conn.Close()

    client, err := smtp.NewClient(conn, mxHost)
    if err != nil {
        return fmt.Errorf("failed to create SMTP client: %v", err)
    }
    defer client.Quit()

    // 3. 发送 HELO 命令
    if err := client.Hello("localhost"); err != nil {
        return fmt.Errorf("failed to say HELO: %v", err)
    }

    // 4. 发送 STARTTLS 命令
    if ok, _ := client.Extension("STARTTLS"); !ok {
        return fmt.Errorf("STARTTLS not supported by %s", mxHost)
    }

    config := &tls.Config{ServerName: mxHost, InsecureSkipVerify: true}
    if err := client.StartTLS(config); err != nil {
        return fmt.Errorf("failed to start TLS: %v", err)
    }

    // 5. 设置发件人和收件人
    if err := client.Mail(from); err != nil {
        return fmt.Errorf("failed to set sender: %v", err)
    }

    if err := client.Rcpt(to); err != nil {
        return fmt.Errorf("failed to set recipient: %v", err)
    }

    // 6. 编写邮件内容，添加Message-ID头
    wc, err := client.Data()
    if err != nil {
        return fmt.Errorf("failed to get write closer: %v", err)
    }

    msgID := generateMessageID(from)
    msg := fmt.Sprintf("Message-ID: %s\r\nFrom: %s\r\nTo: %s\r\nSubject: %s\r\n\r\n%s", msgID, from, to, subject, body)
    _, err = wc.Write([]byte(msg))
    if err != nil {
        return fmt.Errorf("failed to write message: %v", err)
    }

    if err := wc.Close(); err != nil {
        return fmt.Errorf("failed to close write closer: %v", err)
    }

    return nil
}