Form post email to certain users only - php

Question

Anyone can tell why certain emails I put for $email_to will receive the email while other emails I put are unable to receive.
Sorry, a newbie in PHP scripting.
<?php
print "<h2>Simple Contact Form</h2><br/><br/>";
$email_to = "booked#domain.com";
//if "email_from" variable is filled out, send email
if (isset($_REQUEST['email_from'])) {
$email_from = $_REQUEST['email_from'];
$subject = $_REQUEST['subject'];
$comment = $_REQUEST['comment'];
//send email
mail($email_to, "$subject", $comment, "From:" . $email_from);
//Email response
echo "Thank you for contacting us!";
}
//if "email_from" variable is not filled out, display the form
else {
?>
<form method="post">
Email From: <input name="email_from" type="text" /><br />
Subject: <input name="subject" type="text" /><br />
Message:<br />
<textarea name="comment" rows="15" cols="40"></textarea><br />
<input type="submit" value="Submit" />
</form>
<?php
}
?>

Answer 1

You need to use php mailer so that it will work
You must have email address with privilege. Like you hv hosting email...
download phpmailer and add it within your code so that you can send your mail..
here is some rference code which is used by me...
<?php
require("PHPMailer/class.phpmailer.php");
require("PHPMailer/PHPMailerAutoload.php");
define("MAILHOST",'hostsite ');
define("MAILSMTPAuth",true);
define("MAILUsername",'hosting mail');
define("MAILPassword",'password');
define("MAILSMTPSecure",'ssl');
define("MAILPort",portno);
define("MAILFrom",'hosting mail');
$mail = new phpmailer();
$result = array();
$mail->isSMTP(); // Set mailer to use SMTP
$mail->Host = MAILHOST; // Specify main and backup SMTP servers
$mail->SMTPAuth = MAILSMTPAuth; // Enable SMTP authentication
$mail->Username = MAILUsername; // SMTP username
$mail->Password = MAILPassword; // SMTP password
$mail->SMTPSecure = MAILSMTPSecure; // Enable TLS encryption, `ssl` also accepted
$mail->Port = MAILPort; // TCP port to connect to
$mail->From = MAILUsername;
$mail->FromName = 'Name';
$mail->isHTML(true); // Set email format to HTML
$mail->Subject = " Inquiry Form";
$mail->Body = "message";
$mail->SetFrom('hosting mail address', 'name');
$mail->addAddress('recieving mail address', 'Name'); // Add a recipient admin
}
exit;
?>