Preventing developer message to user frontend - laravel-9

Question

I am developing a website with different pages, and among those pages,
I have a contact form that send message to the backend, the email id is unique, I need to display an error message to the front end that if a user enter the email that exist to then it has to display a message the email is taken. How can I go to achieve this. Here is my code
Controller
<?php
namespace App\Http\Controllers\Frontend;
use App\Http\Controllers\Controller;
use Illuminate\Http\Request;
use App\Models\Contact;
use Illuminate\Support\Carbon;
class FrontendPages extends Controller
{
public function About(){
return view('frontend.pages.about');
}//end method
public function Service(){
return view('frontend.pages.services');
}//end method
public function Blog(){
return view('frontend.pages.blog');
}//end method
public function Contact(){
return view('frontend.pages.contact');
}//end method
public function StoreMessage(Request $request){
Contact::insert([
'name' => $request->name,
'email' => $request->email,
'subject' => $request->subject,
'message' => $request->message,
'created_at' =>Carbon::now(),
]);
if ($request->email == 'email') {
return response()->json(['email exist']);
}
$notification = array(
'message' => 'Thank for being in touch we will get back to you soon',
'alert-type' => 'success'
);
return redirect()->back()->with($notification);
}
}
my form
#extends('frontend.main_master')
#section('main')
#php
$footersetup = App\Models\Footer::find(1)->first();
#endphp
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<!-- ======= Breadcrumbs ======= -->
<section id="breadcrumbs" class="breadcrumbs">
<div class="container mt-3">
<div class="d-flex justify-content-between align-items-center">
<h2>Contact</h2>
<ol>
<li>Home</li>
<li>Contact</li>
</ol>
</div>
</div>
</section>
<!-- End Breadcrumbs -->
<!-- ======= Contact Section ======= -->
<section id="contact" class="contact">
<div class="container">
<div class="row mt-5">
<div class="col-lg-4">
<div class="info">
<h4>Location:</h4>
<div class="address">
<i class="bi bi-geo-alt"></i>
{!! $footersetup->address !!}<br /><br />
</div>
<div class="email">
<i class="bi bi-envelope"></i>
<h4>Email:</h4>
<p>
{{$footersetup->email}}<br />{{$footersetup->email1}}
</p>
</div>
<div class="phone">
<i class="bi bi-phone"></i>
<h4>Call:</h4>
<p>{{$footersetup->phone}}</p>
</div>
</div>
</div>
<div class="col-lg-8 mt-5 mt-lg-0">
<form
action="{{route('store.message')}}"
method="post"
role="form"
>
#csrf
<div class="row">
<div class="col-md-6 form-group">
<input
type="text"
name="name"
class="form-control"
id="name"
placeholder="Your Name"
required
/>
</div>
<div class="col-md-6 form-group mt-3 mt-md-0">
<input
type="email"
class="form-control"
name="email"
id="email"
placeholder="Your Email"
required
/>
</div>
</div>
<div class="form-group mt-3">
<input
type="text"
class="form-control"
name="subject"
id="subject"
placeholder="Subject"
required
/>
</div>
<div class="form-group mt-3">
<textarea
class="form-control"
name="message"
rows="5"
placeholder="Message"
required
></textarea>
</div>
<div class="my-3">
</div>
<div class="text-center">
<button type="submit" class="btn btn-success">Send Message</button>
</div>
</form>
</div>
</div>
</div>
</section>
<!-- End Contact Section -->
#endsection