set the email in a loop and the mail function
$subject = "Subject here";
$replyto = "email address";
$message = "Whatever";
while($row = mysql_fetch_array($result)) {
$email = "".$row["email"].",";
}
mail("$email","$subject",'$message","From:$replyto");
I have had to do the same thing before. This will get your started.