diff --git a/backend/app/api/enterprise.py b/backend/app/api/enterprise.py
index 715adf25f..b886ba81c 100644
--- a/backend/app/api/enterprise.py
+++ b/backend/app/api/enterprise.py
@@ -1590,6 +1590,23 @@ def _require_tenant_admin(current_user: User) -> None:
         raise HTTPException(status_code=400, detail="No company assigned")
 
 
+async def _ensure_invitation_email_enabled(db: AsyncSession) -> None:
+    """Require enabled system email before accepting email invitations."""
+    from app.services.system_email_service import resolve_email_config_async
+
+    if await resolve_email_config_async(db):
+        return
+    if await resolve_email_config_async(db, include_disabled=True):
+        raise HTTPException(
+            status_code=400,
+            detail="System email SMTP is configured but disabled. Enable system email before sending invitations.",
+        )
+    raise HTTPException(
+        status_code=400,
+        detail="System email SMTP settings are not configured. Configure system email before sending invitations.",
+    )
+
+
 @router.post("/invitation-codes")
 async def create_invitation_codes(
     data: InvitationCodeCreate,
@@ -1641,6 +1658,8 @@ async def invite_users(
     if not tenant:
         raise HTTPException(status_code=404, detail="Company not found")
 
+    await _ensure_invitation_email_enabled(db)
+
     base_url = await platform_service.get_public_base_url(db, request=request)
     
     invited_count = 0
diff --git a/backend/tests/test_enterprise_invites.py b/backend/tests/test_enterprise_invites.py
new file mode 100644
index 000000000..99e069fb8
--- /dev/null
+++ b/backend/tests/test_enterprise_invites.py
@@ -0,0 +1,59 @@
+import pytest
+from fastapi import HTTPException
+
+from app.api import enterprise as enterprise_api
+from app.services.system_email_service import SystemEmailConfig
+
+
+@pytest.mark.asyncio
+async def test_invitation_email_preflight_rejects_disabled_system_email(monkeypatch):
+    calls = []
+
+    async def fake_resolve_email_config_async(_db, *, include_disabled: bool = False):
+        calls.append(include_disabled)
+        if include_disabled:
+            return SystemEmailConfig(
+                from_address="bot@example.com",
+                from_name="Clawith",
+                smtp_host="smtp.example.com",
+                smtp_port=465,
+                smtp_username="bot@example.com",
+                smtp_password="secret",
+                smtp_ssl=True,
+                smtp_timeout_seconds=15,
+            )
+        return None
+
+    monkeypatch.setattr(
+        "app.services.system_email_service.resolve_email_config_async",
+        fake_resolve_email_config_async,
+    )
+
+    with pytest.raises(HTTPException) as excinfo:
+        await enterprise_api._ensure_invitation_email_enabled(object())
+
+    assert excinfo.value.status_code == 400
+    assert "disabled" in excinfo.value.detail
+    assert calls == [False, True]
+
+
+@pytest.mark.asyncio
+async def test_invitation_email_preflight_accepts_enabled_system_email(monkeypatch):
+    async def fake_resolve_email_config_async(_db, *, include_disabled: bool = False):
+        return SystemEmailConfig(
+            from_address="bot@example.com",
+            from_name="Clawith",
+            smtp_host="smtp.example.com",
+            smtp_port=465,
+            smtp_username="bot@example.com",
+            smtp_password="secret",
+            smtp_ssl=True,
+            smtp_timeout_seconds=15,
+        )
+
+    monkeypatch.setattr(
+        "app.services.system_email_service.resolve_email_config_async",
+        fake_resolve_email_config_async,
+    )
+
+    await enterprise_api._ensure_invitation_email_enabled(object())