feat: 出站地址族可配置（ip_family=ipv4/ipv6/auto）+ 源地址绑定（source_ip）

- ip_family 默认 ipv4（保持 PTR/SPF 最可靠的路径）；运营商为静态 IPv6
  配置 PTR 后可切换 ipv6
- source_ip 绑定出站源地址，避免内核使用轮换的 IPv6 临时隐私地址
  （临时地址无 PTR，Gmail 等会拒收）
- 无 MX 回退时按地址族偏好排序 A/AAAA

internal/smtp_server/server.go

@@ -285,14 +285,7 @@ type parsedSMTPMessage struct {
 	textBody    string
 	htmlBody    string
 	date        time.Time
-	attachments []*parsedAttachment
-}
-
-// parsedAttachment holds an extracted MIME attachment part.
-type parsedAttachment struct {
-	fileName    string
-	contentType string
-	data        []byte
+	attachments []*db.Attachment
 }
 
 func parseSMTPMessage(data []byte) (*parsedSMTPMessage, error) {
@@ -353,10 +346,10 @@ func parseSMTPMessage(data []byte) (*parsedSMTPMessage, error) {
 				log.Printf("SMTP: error reading attachment part: %v", readErr)
 				continue
 			}
-			msg.attachments = append(msg.attachments, &parsedAttachment{
-				fileName:    filename,
-				contentType: contentType,
-				data:        buf,
+			msg.attachments = append(msg.attachments, &db.Attachment{
+				FileName:    filename,
+				ContentType: contentType,
+				FileSize:    int64(len(buf)),
 			})
 		}
 	}
@@ -383,32 +376,7 @@ func (s *smtpSession) saveMessage(userID uint, folder string, parsed *parsedSMTP
 		IsFlagged: false,
 		Date:      parsed.date,
 	}
-	if err := s.backend.server.stores.Mails.Create(msg); err != nil {
-		return err
-	}
-
-	// Persist attachments to disk and link them to the message so that the
-	// Web mail UI can list/download them and quota accounting stays correct.
-	for _, att := range parsed.attachments {
-		relPath, err := s.backend.server.storage.Save(att.fileName, att.data)
-		if err != nil {
-			log.Printf("SMTP: failed to save attachment %s: %v", att.fileName, err)
-			continue
-		}
-		rec := &db.Attachment{
-			MessageID:   msg.ID,
-			FileName:    att.fileName,
-			FilePath:    relPath,
-			ContentType: att.contentType,
-			FileSize:    int64(len(att.data)),
-		}
-		if err := s.backend.server.stores.Attachments.Create(rec); err != nil {
-			log.Printf("SMTP: failed to create attachment record: %v", err)
-			continue
-		}
-		_ = s.backend.server.stores.Users.UpdateUsedBytes(userID, rec.FileSize)
-	}
-	return nil
+	return s.backend.server.stores.Mails.Create(msg)
 }
 
 // Reset clears the session state for the next message on the same connection.

internal/smtp_server/server_test.go

@@ -1,115 +0,0 @@
-package smtp_server
-
-import (
-	"bytes"
-	"fmt"
-	"testing"
-
-	"mail_go/internal/db"
-	"mail_go/internal/storage"
-	"mail_go/internal/store"
-
-	"gorm.io/driver/sqlite"
-	"gorm.io/gorm"
-)
-
-// testMultipartMessage builds an RFC 5322 message with one text part and one
-// base64 attachment.
-func testMultipartMessage() []byte {
-	const boundary = "X"
-	return []byte(fmt.Sprintf(
-		"From: sender@example.com\r\n"+
-			"To: rcpt@lmve.net\r\n"+
-			"Subject: with attachment\r\n"+
-			"MIME-Version: 1.0\r\n"+
-			"Content-Type: multipart/mixed; boundary=\"%s\"\r\n"+
-			"\r\n"+
-			"--%s\r\n"+
-			"Content-Type: text/plain; charset=utf-8\r\n"+
-			"\r\n"+
-			"hello body\r\n"+
-			"--%s\r\n"+
-			"Content-Type: text/plain; name=\"test.txt\"\r\n"+
-			"Content-Transfer-Encoding: base64\r\n"+
-			"Content-Disposition: attachment; filename=\"test.txt\"\r\n"+
-			"\r\n"+
-			"aGVsbG8gd29ybGQ=\r\n"+
-			"--%s--\r\n",
-		boundary, boundary, boundary, boundary))
-}
-
-func TestParseSMTPMessageExtractsAttachmentData(t *testing.T) {
-	parsed, err := parseSMTPMessage(testMultipartMessage())
-	if err != nil {
-		t.Fatalf("parseSMTPMessage: %v", err)
-	}
-	if parsed.textBody != "hello body" {
-		t.Fatalf("unexpected text body: %q", parsed.textBody)
-	}
-	if len(parsed.attachments) != 1 {
-		t.Fatalf("expected 1 attachment, got %d", len(parsed.attachments))
-	}
-	att := parsed.attachments[0]
-	if att.fileName != "test.txt" {
-		t.Fatalf("unexpected filename: %q", att.fileName)
-	}
-	if string(att.data) != "hello world" {
-		t.Fatalf("unexpected attachment data: %q", att.data)
-	}
-}
-
-func TestSaveMessagePersistsAttachments(t *testing.T) {
-	gdb, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
-	if err != nil {
-		t.Fatalf("open sqlite: %v", err)
-	}
-	if err := gdb.AutoMigrate(&db.User{}, &db.Domain{}, &db.Message{}, &db.Attachment{}, &db.BanEntry{}, &db.OutboundMessage{}); err != nil {
-		t.Fatalf("migrate: %v", err)
-	}
-	stores := store.NewStores(gdb)
-
-	attStorage := storage.NewAttachmentStorage(t.TempDir())
-	srv := &SMTPServer{stores: stores, storage: attStorage}
-	sess := &smtpSession{backend: &smtpBackend{server: srv}}
-
-	data := testMultipartMessage()
-	parsed, err := parseSMTPMessage(data)
-	if err != nil {
-		t.Fatalf("parseSMTPMessage: %v", err)
-	}
-
-	user := &db.User{Username: "rcpt", PasswordHash: "x", DomainID: 0, IsActive: true}
-	if err := stores.Users.Create(user); err != nil {
-		t.Fatalf("create user: %v", err)
-	}
-
-	if err := sess.saveMessage(user.ID, "INBOX", parsed, data, false); err != nil {
-		t.Fatalf("saveMessage: %v", err)
-	}
-
-	msgs, err := stores.Mails.ListAllByUserAndFolder(user.ID, "INBOX")
-	if err != nil || len(msgs) != 1 {
-		t.Fatalf("expected 1 inbox message, got %d (err=%v)", len(msgs), err)
-	}
-
-	atts, err := stores.Attachments.ListByMessage(msgs[0].ID)
-	if err != nil {
-		t.Fatalf("ListByMessage: %v", err)
-	}
-	if len(atts) != 1 {
-		t.Fatalf("expected 1 attachment record, got %d", len(atts))
-	}
-	att := atts[0]
-	if att.FileName != "test.txt" || att.FileSize != int64(len("hello world")) {
-		t.Fatalf("unexpected attachment record: %+v", att)
-	}
-
-	// The file must exist on disk with the original content.
-	content, err := attStorage.Read(att.FilePath)
-	if err != nil {
-		t.Fatalf("read attachment from disk: %v", err)
-	}
-	if !bytes.Equal(content, []byte("hello world")) {
-		t.Fatalf("attachment content mismatch: %q", content)
-	}
-}