mail form problem

hi all

got a problem - I've got a form on my front page which simply emails the
entered email address to me - check it out:

http://www.curve-online.co.uk

if you click the mouse on the send button then the mail goes through to me
fine and it thanks the user . If you just press enter then the screen
resets seemingly ok, but there is no thank you and no mail comes through. I
could be losing tons of people here who want to be signed up to my mailing
list...

here's the code - any idea how I can fix this?

thanks

daz



<?php
$Sbjct = "Curve Mailing List";
$Sender = "website@curve-online.co.uk";
if (!$_POST['Submit']){ ?>
<p class="nav"><a
href="http://pub.alxnet.com/guestbook?id=1054509">guestbook</a></p>
<p class="daz">please enter your email below to be added<br />to the
<b>Cuckoo's Nest</b> mailing list</p>
<form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<input type="text" name="Email" size="15" style="width: 200" /><br />
<input type="Submit" name="Submit" value="Send!" />
</form>
<p>(no spam - promise!)</p>
<?php
} else {
$Line1="the following person has signed up:";
mail("mail@curve-online.co.uk","$Sbjct","$Line1\nEmail:
$_POST[email]","From: $Sender");
print "<p>thanks for signing up...</p>";
} ?>