Server overload

Maybe you can help me please. I have this little problem with my 
script. I want send to 300 members send newsletters.

<?php
include("connect.php");

$link=mysql_connect($host,$user,$password);
mysql_select_db($db);

$send_mail_to="SELECT * FROM $newsletter_table";
$send_mail_to_result=mysql_query($send_mail_to);

while($data=mysql_fetch_array($send_mail_to_result))
{
$user_email=$data[1];

mail("$user_email;","blah","From:blah.com");
}
mysql_close($link);
?>

cu,
~g