diff --git a/.changeset/import-email-client-validation.md b/.changeset/import-email-client-validation.md
new file mode 100644
index 000000000..b6ee3dc2c
--- /dev/null
+++ b/.changeset/import-email-client-validation.md
@@ -0,0 +1,15 @@
+---
+"@object-ui/plugin-grid": patch
+---
+
+fix(grid): validate email format in the import preview (objectstack#3566)
+
+The ImportWizard's per-cell `validateValue` did no format check for `email`
+columns (it fell through to `default → true`), so an obviously-bad address —
+e.g. a non-ASCII domain like `x@柴仟.com` — passed client validation (and the
+server dry-run) and only failed at real-import time inside better-auth, giving
+a jarring "passed validation, then failed" experience.
+
+- Added `isPlausibleEmail`, a single-pass structural + ASCII check that mirrors
+  the server's `isLikelyEmail`, so bad emails are flagged red in the preview
+  step before submit. No regex backtracking (same ReDoS-safety as the server).
diff --git a/packages/plugin-grid/src/ImportWizard.tsx b/packages/plugin-grid/src/ImportWizard.tsx
index 371982e16..c061faaba 100644
--- a/packages/plugin-grid/src/ImportWizard.tsx
+++ b/packages/plugin-grid/src/ImportWizard.tsx
@@ -414,12 +414,31 @@ function formatDryRunError(
   return { fieldLabel, message };
 }
 
+/**
+ * Plausible email? Mirrors the server's `isLikelyEmail` (structure + ASCII) so
+ * an obviously-bad address — e.g. a non-ASCII domain like `x@柴仟.com` — is
+ * flagged red in the preview here, instead of passing client + dry-run
+ * validation only to be rejected by better-auth at real-import time
+ * (framework#3566). Deliberately not a regex: a single-pass structural check
+ * has no backtracking (cf. the server-side ReDoS note).
+ */
+export function isPlausibleEmail(value: string): boolean {
+  if (value.length === 0 || value.length > 254 || /\s/.test(value)) return false;
+  if (/[^\x00-\x7f]/.test(value)) return false; // ASCII only, like the server
+  const at = value.indexOf('@');
+  if (at <= 0 || at !== value.lastIndexOf('@') || at === value.length - 1) return false;
+  const domain = value.slice(at + 1);
+  const dot = domain.lastIndexOf('.');
+  return dot > 0 && dot < domain.length - 1;
+}
+
 function validateValue(value: string, type: string): boolean {
   if (!value) return true;
   switch (type) {
     case 'number': case 'currency': case 'percent': return !isNaN(Number(value));
     case 'boolean': return BOOLEAN_IMPORT_TOKENS.has(value.trim().toLowerCase());
     case 'date': case 'datetime': return !isNaN(Date.parse(value));
+    case 'email': return isPlausibleEmail(value.trim());
     default: return true;
   }
 }
diff --git a/packages/plugin-grid/src/importEmailValidation.test.ts b/packages/plugin-grid/src/importEmailValidation.test.ts
new file mode 100644
index 000000000..d0dd731c2
--- /dev/null
+++ b/packages/plugin-grid/src/importEmailValidation.test.ts
@@ -0,0 +1,39 @@
+/**
+ * ObjectUI – Copyright (c) 2024-present ObjectStack Inc.
+ * Licensed under MIT.
+ */
+
+/**
+ * isPlausibleEmail() mirrors the server's `isLikelyEmail` (structure + ASCII)
+ * so obviously-bad addresses fail in the preview step instead of only at
+ * real-import time (framework#3566).
+ */
+import { describe, it, expect } from 'vitest';
+import { isPlausibleEmail } from './ImportWizard';
+
+describe('isPlausibleEmail', () => {
+  it('accepts normal addresses', () => {
+    expect(isPlausibleEmail('name@example.com')).toBe(true);
+    expect(isPlausibleEmail('first.last@sub.example.co')).toBe(true);
+  });
+
+  it('rejects non-ASCII addresses (the reported bug)', () => {
+    expect(isPlausibleEmail('735431496@柴仟.com')).toBe(false);
+    expect(isPlausibleEmail('ａｂｃ@b.com')).toBe(false);
+  });
+
+  it('rejects structurally-broken addresses', () => {
+    expect(isPlausibleEmail('no-at.example.com')).toBe(false);
+    expect(isPlausibleEmail('a@b')).toBe(false);
+    expect(isPlausibleEmail('a@@b.co')).toBe(false);
+    expect(isPlausibleEmail('a@.co')).toBe(false);
+    expect(isPlausibleEmail('a@b.')).toBe(false);
+    expect(isPlausibleEmail('has space@b.co')).toBe(false);
+  });
+
+  it('is fast on adversarial input (no backtracking)', () => {
+    const t0 = Date.now();
+    expect(isPlausibleEmail('!@'.repeat(100_000))).toBe(false);
+    expect(Date.now() - t0).toBeLessThan(1000);
+  });
+});