Function user_notification() excludes banned users' ids from the list of users to be notified, but it doesn't take in account stale bans. This results in effect that users whose bans were expired but not deleted from the banlist table for the moment still won't get email notifications (includes/functions_posting.php, around line 1183):

	// Get banned User ID's

	$sql = 'SELECT ban_userid

		FROM ' . BANLIST_TABLE . '

		WHERE ban_userid <> 0

			AND ban_exclude <> 1';