diff --git a/backend/services/list/imap_search.go b/backend/services/list/imap_search.go
index c103406..14001ce 100644
--- a/backend/services/list/imap_search.go
+++ b/backend/services/list/imap_search.go
@@ -6,6 +6,7 @@ import (
 	"strings"
 	"time"
 
+	"git.pcux.cn/xuans/Smail/config"
 	"git.pcux.cn/xuans/Smail/db"
 	"git.pcux.cn/xuans/Smail/dto/response"
 	"git.pcux.cn/xuans/Smail/models"
@@ -433,6 +434,17 @@ func matchesHeader(email *models.Email, key, value string) bool {
 	value = strings.ToLower(value)
 
 	switch key {
+	case "message-id":
+		messageID := strings.TrimSpace(email.MsgID)
+		if messageID == "" {
+			// 旧邮件使用与 IMAP FETCH 一致的备用标识。
+			cfg := config.CurrentConfig()
+			if cfg == nil || strings.TrimSpace(cfg.Domain) == "" || email.Id <= 0 {
+				return false
+			}
+			messageID = fmt.Sprintf("%d@%s", email.Id, strings.TrimSpace(cfg.Domain))
+		}
+		return strings.Contains(strings.ToLower("<"+messageID+">"), value)
 	case "subject":
 		return strings.Contains(strings.ToLower(email.Subject), value)
 	case "from":
diff --git a/backend/services/list/imap_search_test.go b/backend/services/list/imap_search_test.go
new file mode 100644
index 0000000..54774dc
--- /dev/null
+++ b/backend/services/list/imap_search_test.go
@@ -0,0 +1,67 @@
+package list
+
+import (
+	"fmt"
+	"testing"
+
+	"git.pcux.cn/xuans/Smail/config"
+	"git.pcux.cn/xuans/Smail/db"
+	"git.pcux.cn/xuans/Smail/models"
+	"git.pcux.cn/xuans/Smail/utils/context"
+	"github.com/emersion/go-imap/v2"
+)
+
+func TestSearchEmailsMessageID(t *testing.T) {
+	initListTestDB(t)
+	config.Instance.Domain = "example.test"
+	matching := models.Email{MsgID: "Public-Receipt@example.test", Subject: "matching"}
+	foreign := models.Email{MsgID: matching.MsgID, Subject: "foreign"}
+	legacy := models.Email{Subject: "legacy"}
+	if _, err := db.Instance.Insert(&matching, &foreign, &legacy); err != nil {
+		t.Fatal(err)
+	}
+	inbox := models.UserEmail{UserID: 1, EmailID: matching.Id}
+	otherUser := models.UserEmail{UserID: 2, EmailID: foreign.Id}
+	legacyInbox := models.UserEmail{UserID: 1, EmailID: legacy.Id}
+	if _, err := db.Instance.Insert(&inbox, &otherUser, &legacyInbox); err != nil {
+		t.Fatal(err)
+	}
+	for _, test := range []struct {
+		name  string
+		value string
+		want  int
+	}{
+		{name: "full header", value: "<Public-Receipt@example.test>", want: inbox.ID},
+		{name: "case insensitive", value: "<PUBLIC-RECEIPT@EXAMPLE.TEST>", want: inbox.ID},
+		{name: "substring", value: "receipt@", want: inbox.ID},
+		{name: "legacy fallback", value: fmt.Sprintf("<%d@example.test>", legacy.Id), want: legacyInbox.ID},
+		{name: "absent value", value: "<missing@example.test>"},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			criteria := &imap.SearchCriteria{Header: []imap.SearchCriteriaHeaderField{{Key: "mEsSaGe-Id", Value: test.value}}}
+			rows, err := SearchEmails(&context.Context{UserID: 1}, "INBOX", criteria)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if test.want == 0 {
+				if len(rows) != 0 {
+					t.Fatalf("unexpected matches: %#v", rows)
+				}
+			} else if len(rows) != 1 || rows[0].ID != test.want {
+				t.Fatalf("matches = %#v, want only relation %d", rows, test.want)
+			}
+		})
+	}
+}
+
+func TestMessageIDHeaderPresence(t *testing.T) {
+	previous := config.Instance
+	config.Instance = nil
+	t.Cleanup(func() { config.Instance = previous })
+	if matchesHeader(&models.Email{}, "Message-ID", "") {
+		t.Fatal("missing header must not match an empty search value")
+	}
+	if !matchesHeader(&models.Email{MsgID: "stored@example.test"}, "Message-ID", "") {
+		t.Fatal("stored header must match an empty search value")
+	}
+}