php mail()函数不起作用

Php mail()对我不起作用.
我已经用Google搜索出解决方案，但对我没有用.

有人可以帮忙吗?
这是我的代码:-

Php mail() is not working for me.
I have google out the solutions, but doesn''t worked for me.

Can anybody please help??
Here is my code :-

<?php
$conn = mysql_connect($dbhost, $dbuser, $dbpass) or die('Error connecting to mysql');
mysql_select_db($dbname);

$query = "select * from homework_reminders";
$rs = mysql_query($query);
while($row = mysql_fetch_array($rs)){
	$subject = $row['tx_title'];
	$message = $row['tx_description'];
	$message = wordwrap($message, 70);
	$headers = "From: abc@gmail.com";
	$reminder_sent = $row["nu_reminder_sent"] + 1;
	if(($row['da_reminder'] == date('Y-m-d')) && ($row["nu_no_of_reminder"] != $reminder_sent)){
		if(mail('khushboo.chaturvedi@narolainfotech.com', $subject, $message, $headers)){
			$dt = date('Y-m-d');
			$update_query = "UPDATE homework_reminders SET nu_reminder_sent = ".$reminder_sent." WHERE da_reminder = '.$dt.'";
			mysql_query($update_query);
			echo "Mail send";
		}
	}
}
?>