Follow these easy instructions:
----
? At the top of AP_Broadcast_Email, right after this code:
define('PUN_PLUGIN_LOADED', 1);? Add this:
include PUN_ROOT."include/email.php";? Then find this code:
while($row = $db->fetch_assoc($result))
{
$addresses[$row['username']] = $row['email'];
}? Replace it with this code:
while($row = $db->fetch_assoc($result))
{
if(!is_valid_email($row['email']))
continue;
$addresses[$row['username']] = $row['email'];
}----
I think that should do the trick 
You should use the check_valid_email() function in include/email.php.
Well, not standard that is.