No mail were delivered when used mail.php [duplicate]

I have Index.html where i have created the form with some basic fields

<form class="modal-content animate" action="mail.php" method="post">


        <div class="container-form">
          <label for="full_Name"><b>Full Name</b></label>
          <input type="text" placeholder="Full Name" id="full_Name" name="full_Name" required>

          <label for="telephone_Number"><b>Mobile Number</b></label>
          <input type="text" placeholder="Mobile Number" name="telephone_Number" required>

          <label for="message"><b>Email Id</b></label>
          <input type="text" placeholder="Email Id" name="email_Address" required>
          <button type="submit" name = "submit" id="submit" class="read-more">Submit</button>
        </div>
      </form>

and i have include mail.php

<?php 
if(isset($_POST['submit'])){
    $to = $_POST['email_Address']; // this is your Email address
    $from = $_POST['xyz@gmail.com']; // this is the sender's Email address
    $full_Name = $_POST['full_Name'];
    $telephone_Number = $_POST['telephone_Number'];
    $subject = "Form submission";
    $message = " Dear". "$full_Name . ". "Thanks for contacting " . $telephone_Number . " wrote the following:" . "\n\n" . $_POST['message'];

    $headers[] = 'MIME-Version: 1.0';
    $headers[] = 'Content-type: text/html; charset=iso-8859-1';

    // Additional headers . Your to email id.
    $headers[] = 'From:  <'.$from.'>'; 

    // If you want to add To, Cc and Bcc use this additional headers
    $headers[] = 'To: <'.$to.'>'; 

// Mail it
mail($to, $subject, $message, implode("\r\n", $headers));
    echo "Mail Sent. Thank you " . $first_name . ", we will contact you shortly.";
    // You can also use header('Location: thank_you.php'); to redirect to another page.
    // You cannot use header and echo together. It's one or the other.
    }
?>

but when i click on submit button It shows "Mail Sent. Thank you, we will contact you shortly." but was not received any mail.