244 lines
6.6 KiB
Go
244 lines
6.6 KiB
Go
package smtpclient
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import (
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"crypto/tls"
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"encoding/base64"
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"fmt"
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"net"
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"net/smtp"
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"strings"
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"time"
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)
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// Message 邮件消息
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type Message struct {
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From string // 发件人
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To []string // 收件人列表
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Subject string // 主题
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Body string // 正文（纯文本）
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HTML string // HTML正文（可选）
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}
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// Client SMTP客户端
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type Client struct {
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domain string // 本地域名
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}
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// NewClient 创建SMTP客户端
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func NewClient(domain string) *Client {
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return &Client{domain: domain}
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}
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// Send 发送邮件（通过查找MX记录直接发送）
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func (c *Client) Send(msg Message) error {
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// 验证发件人地址
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if msg.From == "" {
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return fmt.Errorf("发件人地址不能为空")
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}
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// 构建邮件内容
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body := c.buildMessage(msg)
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// 按收件人域名分组发送
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recipientsByDomain := make(map[string][]string)
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for _, to := range msg.To {
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domain := extractDomain(to)
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if domain == "" {
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return fmt.Errorf("无效的收件人地址: %s", to)
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}
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recipientsByDomain[domain] = append(recipientsByDomain[domain], to)
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}
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// 向每个域名发送邮件
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var lastErr error
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for domain, recipients := range recipientsByDomain {
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if err := c.sendToDomain(domain, msg.From, recipients, body); err != nil {
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// 简化错误提示
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errMsg := strings.ToLower(err.Error())
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// 检测常见的拒绝原因
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if strings.Contains(errMsg, "not authorized") ||
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strings.Contains(errMsg, "blocked") ||
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strings.Contains(errMsg, "spamhaus") ||
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strings.Contains(errMsg, "relay") {
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// 国际邮箱拒绝
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if domain == "gmail.com" || domain == "googlemail.com" {
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lastErr = fmt.Errorf("Gmail 拒绝，建议用 QQ/163")
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} else if domain == "outlook.com" || domain == "hotmail.com" || domain == "live.com" {
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lastErr = fmt.Errorf("Outlook 拒绝，建议用 QQ/163")
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} else {
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lastErr = fmt.Errorf("对方拒绝接收（IP 被限制）")
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}
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} else if strings.Contains(errMsg, "连接失败") || strings.Contains(errMsg, "timeout") {
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lastErr = fmt.Errorf("连接超时，请稍后重试")
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} else if strings.Contains(errMsg, "无效") {
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lastErr = fmt.Errorf("收件人地址无效")
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} else {
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// 其他错误，提供通用提示
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lastErr = fmt.Errorf("发送失败，建议用 QQ/163")
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}
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// 继续尝试其他域名
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}
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}
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return lastErr
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}
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// sendToDomain 向指定域名发送邮件
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func (c *Client) sendToDomain(domain string, from string, to []string, body string) error {
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// 查找MX记录
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mxRecords, err := net.LookupMX(domain)
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if err != nil || len(mxRecords) == 0 {
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// 如果没有MX记录，尝试使用A记录
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return c.sendToHost(domain+":25", from, to, body)
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}
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// 尝试每个MX记录（按优先级排序）
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var lastErr error
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for _, mx := range mxRecords {
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host := strings.TrimSuffix(mx.Host, ".")
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if err := c.sendToHost(host+":25", from, to, body); err == nil {
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return nil
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} else {
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lastErr = err // 只保留最后一个错误
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}
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}
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return lastErr
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}
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// sendToHost 向指定主机发送邮件
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func (c *Client) sendToHost(addr string, from string, to []string, body string) error {
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// 连接到SMTP服务器
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client, err := smtp.Dial(addr)
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if err != nil {
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return fmt.Errorf("连接失败 %s: %w", addr, err)
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}
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defer client.Close()
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// 发送HELO命令
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if err = client.Hello(c.domain); err != nil {
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return fmt.Errorf("HELO失败 (domain=%s): %w", c.domain, err)
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}
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// 尝试升级到 TLS（如果服务器支持）
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if ok, _ := client.Extension("STARTTLS"); ok {
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tlsConfig := &tls.Config{
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ServerName: strings.Split(addr, ":")[0],
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InsecureSkipVerify: false, // 验证证书
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}
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if err = client.StartTLS(tlsConfig); err != nil {
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// TLS 失败不致命，继续尝试明文发送
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// 但记录日志便于调试
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// log.Printf("STARTTLS 失败，继续使用明文: %v", err)
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}
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}
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// 设置发件人
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if err = client.Mail(from); err != nil {
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return fmt.Errorf("MAIL FROM失败 (from=%s): %w", from, err)
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}
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// 设置收件人
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for _, recipient := range to {
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if err = client.Rcpt(recipient); err != nil {
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return fmt.Errorf("RCPT TO失败 (to=%s): %w", recipient, err)
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}
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}
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// 发送邮件内容
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w, err := client.Data()
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if err != nil {
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return fmt.Errorf("DATA命令失败: %w", err)
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}
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_, err = w.Write([]byte(body))
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if err != nil {
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w.Close()
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return fmt.Errorf("写入邮件内容失败: %w", err)
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}
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if err = w.Close(); err != nil {
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return fmt.Errorf("关闭DATA失败: %w", err)
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}
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// 退出
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return client.Quit()
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}
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// extractDomain 从邮件地址中提取域名
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func extractDomain(email string) string {
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parts := strings.Split(email, "@")
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if len(parts) != 2 {
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return ""
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}
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return parts[1]
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}
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// buildMessage 构建邮件内容
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func (c *Client) buildMessage(msg Message) string {
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var sb strings.Builder
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// 邮件头
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sb.WriteString(fmt.Sprintf("From: %s\r\n", msg.From))
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sb.WriteString(fmt.Sprintf("To: %s\r\n", strings.Join(msg.To, ", ")))
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sb.WriteString(fmt.Sprintf("Subject: %s\r\n", encodeSubject(msg.Subject)))
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sb.WriteString(fmt.Sprintf("Date: %s\r\n", time.Now().Format(time.RFC1123Z)))
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sb.WriteString("MIME-Version: 1.0\r\n")
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// 如果有HTML内容，使用multipart
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if msg.HTML != "" {
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boundary := fmt.Sprintf("boundary_%d", time.Now().Unix())
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sb.WriteString(fmt.Sprintf("Content-Type: multipart/alternative; boundary=\"%s\"\r\n", boundary))
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sb.WriteString("\r\n")
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// 纯文本部分
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if msg.Body != "" {
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sb.WriteString(fmt.Sprintf("--%s\r\n", boundary))
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sb.WriteString("Content-Type: text/plain; charset=UTF-8\r\n")
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sb.WriteString("Content-Transfer-Encoding: quoted-printable\r\n")
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sb.WriteString("\r\n")
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sb.WriteString(msg.Body)
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sb.WriteString("\r\n")
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}
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// HTML部分
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sb.WriteString(fmt.Sprintf("--%s\r\n", boundary))
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sb.WriteString("Content-Type: text/html; charset=UTF-8\r\n")
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sb.WriteString("Content-Transfer-Encoding: quoted-printable\r\n")
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sb.WriteString("\r\n")
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sb.WriteString(msg.HTML)
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sb.WriteString("\r\n")
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sb.WriteString(fmt.Sprintf("--%s--\r\n", boundary))
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} else {
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// 只有纯文本
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sb.WriteString("Content-Type: text/plain; charset=UTF-8\r\n")
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sb.WriteString("Content-Transfer-Encoding: quoted-printable\r\n")
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sb.WriteString("\r\n")
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sb.WriteString(msg.Body)
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}
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return sb.String()
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}
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// encodeSubject 编码邮件主题（支持中文）
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func encodeSubject(subject string) string {
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// 检查是否包含非ASCII字符
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needEncode := false
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for _, r := range subject {
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if r > 127 {
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needEncode = true
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break
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}
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}
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if !needEncode {
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return subject
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}
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// 使用Base64编码
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encoded := base64.StdEncoding.EncodeToString([]byte(subject))
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return fmt.Sprintf("=?UTF-8?B?%s?=", encoded)
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}
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