Mira este es mi codigo de php:
 
<?php
$nombre = $_REQUEST["txtMonto"];
$email = $_REQUEST["txtMonto2"];
$tema = $_REQUEST["txtMonto3"];
$mensaje = $_REQUEST["txtMonto6"];
$sender = $_REQUEST["sender"];
$message= "DATOS PERSONALES\n\nNombre: " .$nombre."\nE mail: " .$email. "\nTema: " .$tema."\nMensaje: " .$mensaje.  
// remove the backslashes that normally appears when entering " or '
$message = stripslashes($message); 
$subject = stripslashes($subject); 
$sender = stripslashes("Cliente AISecurity");  
// add a prefix in the subject line so that you know the email was sent by online form
$subject = "Solicitud para AISecurity".$subject; 
// send the email, make sure you replace 
[email protected] with your email address
if(isset($message) and isset($subject) and isset($sender)){
	mail("
[email protected]", $subject, $message, "From: $sender");
} 
?> 
Dónde debo de poner la condicional que me diste GatorV ? o la pongo en el formulario..?