if(preg_match("/[A-Za-z0-9_.-]+@([A-Za-z0-9_]+\)+[A-Za-z]{2,4}/i", $_POST[text])) 
{
}
else
{
echo "<script>alert('Mail Adresinizi DüzgüN Yazin')</script>"; echo "<script>javascript:history.back();</script>"; exit();
}