fix(email): report a missing sender address from the SMTP connection test

TestConnection skipped the empty-from guard that Send enforces, so with
no sender and no username configured the test issued the null reverse-path
and could report success against a lenient relay while every real
notification send kept failing with the missing-sender error. Guard the
test path the same way and surface a dedicated translated message.

internal/web/service/email/email.go

@@ -117,6 +117,9 @@ func (s *EmailService) TestConnection() SMTPTestResult {
 	if from == "" {
 		from = username
 	}
+	if from == "" {
+		return SMTPTestResult{false, "send", "smtpFromNotConfigured"}
+	}
 	from, fromName = resolveFrom(from, fromName)
 
 	recipients := parseRecipients(toStr)

internal/web/service/email/email_test.go

@@ -180,6 +180,31 @@ func TestSendUsesBareAddressFromNameAddrSmtpFrom(t *testing.T) {
 	}
 }
 
+func TestConnectionReportsMissingFrom(t *testing.T) {
+	if err := database.InitDB(filepath.Join(t.TempDir(), "x-ui.db")); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = database.CloseDB() })
+
+	settingService := service.SettingService{}
+	mustSet := func(name string, err error) {
+		t.Helper()
+		if err != nil {
+			t.Fatalf("set %s: %v", name, err)
+		}
+	}
+	mustSet("host", settingService.SetSmtpHost("127.0.0.1"))
+	mustSet("port", settingService.SetSmtpPort(1))
+	mustSet("to", settingService.SetSmtpTo("[email protected]"))
+	mustSet("encryption", settingService.SetSmtpEncryptionType("none"))
+
+	got := NewEmailService(settingService).TestConnection()
+	want := SMTPTestResult{Success: false, Stage: "send", Message: "smtpFromNotConfigured"}
+	if got != want {
+		t.Errorf("TestConnection() = %+v, want %+v", got, want)
+	}
+}
+
 func TestBuildMessageStripsHeaderInjection(t *testing.T) {
 	raw := buildMessage(
 		"[email protected]\r\nBcc: [email protected]",

internal/web/translation/ar-EG.json

@@ -1410,6 +1410,7 @@
       "smtpTestSuccess": "تم إرسال البريد التجريبي بنجاح",
       "smtpHostNotConfigured": "خادم SMTP غير مهيأ",
       "smtpNoRecipients": "لا يوجد مستلمون مهيؤون",
+      "smtpFromNotConfigured": "عنوان مرسل SMTP غير مُهيأ",
       "eventLoginAttempt": "محاولة تسجيل دخول",
       "telegramTokenConfigured": "مهيأ؛ اتركه فارغاً للاحتفاظ بالتوكن الحالي.",
       "telegramTokenPlaceholder": "مهيأ — أدخل توكن جديد لاستبداله",

internal/web/translation/en-US.json

@@ -1529,6 +1529,7 @@
       "smtpTestSuccess": "Test email sent successfully",
       "smtpHostNotConfigured": "SMTP host not configured",
       "smtpNoRecipients": "No recipients configured",
+      "smtpFromNotConfigured": "SMTP sender address not configured",
       "eventLoginAttempt": "Login attempt",
       "telegramTokenConfigured": "Configured; leave blank to keep current token.",
       "telegramTokenPlaceholder": "Configured - enter a new token to replace",

internal/web/translation/es-ES.json

@@ -1410,6 +1410,7 @@
       "smtpTestSuccess": "Correo de prueba enviado correctamente",
       "smtpHostNotConfigured": "Servidor SMTP no configurado",
       "smtpNoRecipients": "No hay destinatarios configurados",
+      "smtpFromNotConfigured": "La dirección del remitente SMTP no está configurada",
       "eventLoginAttempt": "Intento de inicio de sesión",
       "telegramTokenConfigured": "Configurado; deje en blanco para mantener el token actual.",
       "telegramTokenPlaceholder": "Configurado: introduzca un nuevo token para reemplazarlo",

internal/web/translation/fa-IR.json

@@ -1412,6 +1412,7 @@
       "smtpTestSuccess": "ایمیل آزمایشی با موفقیت ارسال شد",
       "smtpHostNotConfigured": "میزبان SMTP پیکربندی نشده است",
       "smtpNoRecipients": "هیچ گیرنده‌ای پیکربندی نشده است",
+      "smtpFromNotConfigured": "آدرس فرستنده SMTP پیکربندی نشده است",
       "eventLoginAttempt": "تلاش برای ورود",
       "telegramTokenConfigured": "پیکربندی شده؛ برای حفظ توکن فعلی خالی بگذارید.",
       "telegramTokenPlaceholder": "پیکربندی شده - برای جایگزینی، توکن جدید وارد کنید",

internal/web/translation/id-ID.json

@@ -1410,6 +1410,7 @@
       "smtpTestSuccess": "Email uji berhasil dikirim",
       "smtpHostNotConfigured": "Host SMTP belum dikonfigurasi",
       "smtpNoRecipients": "Tidak ada penerima yang dikonfigurasi",
+      "smtpFromNotConfigured": "Alamat pengirim SMTP belum dikonfigurasi",
       "eventLoginAttempt": "Percobaan masuk",
       "telegramTokenConfigured": "Terkonfigurasi; kosongkan untuk mempertahankan token saat ini.",
       "telegramTokenPlaceholder": "Terkonfigurasi - masukkan token baru untuk mengganti",

internal/web/translation/ja-JP.json

@@ -1410,6 +1410,7 @@
       "smtpTestSuccess": "テストメールを正常に送信しました",
       "smtpHostNotConfigured": "SMTPホストが設定されていません",
       "smtpNoRecipients": "受信者が設定されていません",
+      "smtpFromNotConfigured": "SMTP送信者アドレスが設定されていません",
       "eventLoginAttempt": "ログイン試行",
       "telegramTokenConfigured": "設定済み。現在のトークンを維持する場合は空欄のままにしてください。",
       "telegramTokenPlaceholder": "設定済み - 置き換えるには新しいトークンを入力してください",

internal/web/translation/pt-BR.json

@@ -1410,6 +1410,7 @@
       "smtpTestSuccess": "E-mail de teste enviado com sucesso",
       "smtpHostNotConfigured": "Servidor SMTP não configurado",
       "smtpNoRecipients": "Nenhum destinatário configurado",
+      "smtpFromNotConfigured": "Endereço do remetente SMTP não configurado",
       "eventLoginAttempt": "Tentativa de login",
       "telegramTokenConfigured": "Configurado; deixe em branco para manter o token atual.",
       "telegramTokenPlaceholder": "Configurado - insira um novo token para substituir",

internal/web/translation/ru-RU.json

@@ -1410,6 +1410,7 @@
       "smtpTestSuccess": "Тестовое письмо отправлено успешно",
       "smtpHostNotConfigured": "SMTP хост не настроен",
       "smtpNoRecipients": "Получатели не настроены",
+      "smtpFromNotConfigured": "Адрес отправителя SMTP не настроен",
       "eventLoginAttempt": "Попытка входа",
       "telegramTokenConfigured": "Настроен; оставьте пустым для сохранения текущего токена.",
       "telegramTokenPlaceholder": "Настроен - введите новый токен для замены",

internal/web/translation/tr-TR.json

@@ -1410,6 +1410,7 @@
       "smtpTestSuccess": "Test e-postası başarıyla gönderildi",
       "smtpHostNotConfigured": "SMTP sunucusu yapılandırılmamış",
       "smtpNoRecipients": "Yapılandırılmış alıcı yok",
+      "smtpFromNotConfigured": "SMTP gönderen adresi yapılandırılmamış",
       "eventLoginAttempt": "Oturum açma denemesi",
       "telegramTokenConfigured": "Yapılandırıldı; mevcut belirteci korumak için boş bırakın.",
       "telegramTokenPlaceholder": "Yapılandırıldı - değiştirmek için yeni bir belirteç girin",

internal/web/translation/uk-UA.json

@@ -1410,6 +1410,7 @@
       "smtpTestSuccess": "Тестовий лист успішно надіслано",
       "smtpHostNotConfigured": "Хост SMTP не налаштовано",
       "smtpNoRecipients": "Отримувачів не налаштовано",
+      "smtpFromNotConfigured": "Адресу відправника SMTP не налаштовано",
       "eventLoginAttempt": "Спроба входу",
       "telegramTokenConfigured": "Налаштовано; залиште порожнім, щоб зберегти поточний токен.",
       "telegramTokenPlaceholder": "Налаштовано — введіть новий токен для заміни",

internal/web/translation/vi-VN.json

@@ -1410,6 +1410,7 @@
       "smtpTestSuccess": "Đã gửi email thử nghiệm thành công",
       "smtpHostNotConfigured": "Chưa cấu hình máy chủ SMTP",
       "smtpNoRecipients": "Chưa cấu hình người nhận",
+      "smtpFromNotConfigured": "Chưa cấu hình địa chỉ người gửi SMTP",
       "eventLoginAttempt": "Lần thử đăng nhập",
       "telegramTokenConfigured": "Đã cấu hình; để trống để giữ token hiện tại.",
       "telegramTokenPlaceholder": "Đã cấu hình - nhập token mới để thay thế",

internal/web/translation/zh-CN.json

@@ -1410,6 +1410,7 @@
       "smtpTestSuccess": "测试邮件发送成功",
       "smtpHostNotConfigured": "尚未配置 SMTP 主机",
       "smtpNoRecipients": "尚未配置收件人",
+      "smtpFromNotConfigured": "未配置 SMTP 发件人地址",
       "eventLoginAttempt": "登录尝试",
       "telegramTokenConfigured": "已配置；留空则保留当前令牌。",
       "telegramTokenPlaceholder": "已配置——输入新令牌以替换",

internal/web/translation/zh-TW.json

@@ -1410,6 +1410,7 @@
       "smtpTestSuccess": "測試郵件已成功傳送",
       "smtpHostNotConfigured": "尚未設定 SMTP 主機",
       "smtpNoRecipients": "尚未設定收件人",
+      "smtpFromNotConfigured": "未設定 SMTP 寄件人地址",
       "eventLoginAttempt": "登入嘗試",
       "telegramTokenConfigured": "已設定；留空以保留目前的權杖。",
       "telegramTokenPlaceholder": "已設定 - 輸入新權杖以取代",