PHP mail with SMTP authentication using Pear Mail

If you are using php, then you can use php PEAR mail package authenticate.
This needs PEAR Mail installed along with PHP in the server.

Example Code:
<?php
require_once "Mail.php";

$from = "sender@example.com";
$to = "recipient@example.com";
$subject = "Hi";
$body = "Hi, How are you?";

$host = "example.com";
$username = "smtp_username";
$password = "smtp_password";

$headers = array ('From' => $from, 'To' => $to, 'Subject' => $subject);
$smtp = Mail::factory('smtp',
array ('host' => $host,
'auth' => true,
'username' => $username,
'password' => $password));

$mail = $smtp->send($to, $headers, $body);

if (PEAR::isError($mail)) {
echo("<p>" . $mail->getMessage() . "</p>");
} else {
echo("<p>Message successfully sent!</p>");
}