diff --git a/frontend/src/views/Login.test.ts b/frontend/src/views/Login.test.ts
index ac5cd5c0..cee0538a 100644
--- a/frontend/src/views/Login.test.ts
+++ b/frontend/src/views/Login.test.ts
@@ -96,12 +96,17 @@ describe("Login protocol agreement", () => {
     expect(source).toContain("max-width: calc(100vw - 40px);");
   });
 
-  it("uses only server-configured email domains on web and desktop", () => {
+  it("falls back to full email input when no server-configured domains exist", () => {
     const source = readLoginView();
 
     expect(source).toContain('fetchEmailDomains()');
-    expect(source).toContain(':disabled="availableEmailDomains.length === 0"');
     expect(source).toContain("const availableEmailDomains = computed(() => configuredEmailDomains.value)");
+    expect(source).toContain("availableEmailDomains.value.length > 0 && availableEmailDomains.value.includes(form.emailDomain)");
+    expect(source).toContain("const manualEmailInput = computed(() => !hasConfiguredEmailDomains.value)");
+    expect(source).toContain('v-if="hasConfiguredEmailDomains"');
+    expect(source).toContain("未检测到邮箱后缀配置，请输入完整邮箱地址。");
+    expect(source).toContain("form.email = local;");
+    expect(source).toContain("if (domains.length === 0)");
     expect(source).toContain("configuredEmailDomains.value.includes(domain)");
     expect(source).not.toContain("preservedEmailDomain");
     expect(source).not.toContain("showDomainSelect");
diff --git a/frontend/src/views/Login.vue b/frontend/src/views/Login.vue
index 1ce337fa..47e67319 100644
--- a/frontend/src/views/Login.vue
+++ b/frontend/src/views/Login.vue
@@ -145,19 +145,19 @@
           <!-- 登录表单 -->
           <el-form ref="formRef" :model="form" :rules="rules" @keyup.enter="onSubmit" label-position="top" class="login-form">
             <el-form-item label="账号" prop="email">
-              <div class="email-unified-box">
+              <div class="email-unified-box" :class="{ 'email-unified-box--manual': manualEmailInput }">
                 <input
                   id="email"
                   v-model="form.emailLocal"
-                  type="text"
-                  placeholder="请输入账号"
+                  :type="manualEmailInput ? 'email' : 'text'"
+                  :placeholder="emailInputPlaceholder"
                   name="username"
                   autocomplete="username"
                   class="email-local-field"
                   @paste="handleAccountPaste"
                 />
-                <span class="email-at-sign">@</span>
-                <div class="email-domain-wrapper">
+                <span v-if="hasConfiguredEmailDomains" class="email-at-sign">@</span>
+                <div v-if="hasConfiguredEmailDomains" class="email-domain-wrapper">
                   <select
                     v-model="form.emailDomain"
                     class="email-domain-field"
@@ -169,6 +169,7 @@
                   <svg class="email-domain-chevron" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5"><path d="m6 9 6 6 6-6"/></svg>
                 </div>
               </div>
+              <p v-if="manualEmailInput" class="email-manual-hint">未检测到邮箱后缀配置，请输入完整邮箱地址。</p>
             </el-form-item>
 
             <el-form-item label="密码" prop="password">
@@ -294,9 +295,19 @@ const refreshDesktopServerUrl = () => {
 
 const normalizeDomain = (value: string) => value.trim().toLowerCase().replace(/^@/, "");
 const availableEmailDomains = computed(() => configuredEmailDomains.value);
+const hasConfiguredEmailDomains = computed(() =>
+  availableEmailDomains.value.length > 0 && availableEmailDomains.value.includes(form.emailDomain)
+);
+const manualEmailInput = computed(() => !hasConfiguredEmailDomains.value);
+const emailInputPlaceholder = computed(() => manualEmailInput.value ? "请输入完整邮箱" : "请输入账号");
 
 const syncEmailFromParts = () => {
   const local = form.emailLocal.trim().toLowerCase();
+  if (manualEmailInput.value) {
+    form.emailDomain = "";
+    form.email = local;
+    return;
+  }
   const domain = normalizeDomain(form.emailDomain);
   form.emailDomain = domain;
   form.email = local && domain ? `${local}@${domain}` : "";
@@ -304,6 +315,12 @@ const syncEmailFromParts = () => {
 
 const applyEmailValue = (email: string) => {
   const normalized = email.trim().toLowerCase();
+  if (availableEmailDomains.value.length === 0) {
+    form.emailLocal = normalized;
+    form.emailDomain = "";
+    syncEmailFromParts();
+    return;
+  }
   const separator = normalized.lastIndexOf("@");
   if (separator > 0) {
     form.emailLocal = normalized.slice(0, separator);
@@ -321,16 +338,32 @@ const applyEmailValue = (email: string) => {
 const loadEmailDomains = async () => {
   try {
     const { data } = await fetchEmailDomains();
-    configuredEmailDomains.value = Array.from(new Set(
-      data.items.map(normalizeDomain).filter(Boolean)
+    const domains = Array.from(new Set(
+      (Array.isArray(data.items) ? data.items : [])
+        .map(item => typeof item === "string" ? normalizeDomain(item) : "")
+        .filter(Boolean)
     ));
-    if (!configuredEmailDomains.value.includes(form.emailDomain)) {
-      form.emailDomain = configuredEmailDomains.value[0] || "";
+    configuredEmailDomains.value = domains;
+
+    if (domains.length === 0) {
+      form.emailDomain = "";
+      syncEmailFromParts();
+      return;
+    }
+
+    if (form.emailLocal.includes("@")) {
+      applyEmailValue(form.emailLocal);
+      return;
+    }
+
+    if (!domains.includes(form.emailDomain)) {
+      form.emailDomain = domains[0];
     }
   } catch {
     configuredEmailDomains.value = [];
     form.emailDomain = "";
   }
+  syncEmailFromParts();
 };
 
 const handleAccountPaste = (event: ClipboardEvent) => {
@@ -367,6 +400,7 @@ const confirmProtocol = () => { form.agreeProtocol = true; protocolDialogVisible
 
 const onSubmit = async () => {
   if (!formRef.value) return;
+  syncEmailFromParts();
   const valid = await formRef.value.validate();
   if (!valid) return;
   if (!form.agreeProtocol) { ElMessage.warning("请先阅读并同意用户协议"); return; }
@@ -948,6 +982,10 @@ const onSubmit = async () => {
   border-bottom-color: #2563eb;
 }
 
+.email-unified-box--manual .email-local-field {
+  width: 100%;
+}
+
 .email-local-field,
 .email-domain-field {
   min-width: 0;
@@ -969,6 +1007,13 @@ const onSubmit = async () => {
   color: #94a3b8;
 }
 
+.email-manual-hint {
+  margin: 8px 0 0;
+  color: #64748b;
+  font-size: 12px;
+  line-height: 1.5;
+}
+
 .email-at-sign {
   flex-shrink: 0;
   padding: 0 4px;