Using form method=post with wordpress

I am trying to integrate a ‘subscribe to newsletter’ feature on my wordpress blog

Users just need to enter their name and email address, hit subscribe. This is then supposed to send me an email and I add them to the mailing list.

I activated the WP SMTP Mail plugin and entered in the relevant email server information to enable WordPress to send emails, asked WordPress to send me a test message and this worked.

Now I want to receive an email whenever someone fills in their name & email and hit subscribe.

If I do this at the moment it just takes me to newsletter_signup.php and I get at error message saying…

‘NOT FOUND Apologies, but no results were found for the requested post.’
Obviously this is not right and no email is being sent/received.

I have attached my code below, can anyone help me out here?

Thanks

Code for the signup form sidebar.php – This is not a plugin.

<form action="newsletter_signup.php" method="post">
<p><input class="full" type="text" name="fullname" placeholder="Your name*"></p>
   <p><input class="full" type="email" name="Email" placeholder="Your email                                    address*"></p>
<p><input type="submit" class="sub-btn" value="Subscribe"></p>
                        </form>

newsletter_signup.php

<?php
$fullname = $_POST['name'];
$Email = $_POST['Email'];

$to = 'me@myself.com';      

wp_mail($to, $fullname, 'From: ' . $Email);
echo 'Your request Has Been Sent, Thank You. ';

?>