If you are getting too much spam, the first thing we recommend is making your Spam Protection more aggressive. Go to the Home page and move your slider up to increase the aggressiveness of your settings.
If you are forwarding mail to your Pobox account from another domain, we might also be ignoring some of your spam. Many of our filters check the place that sent us the message (the sending domain). So, for instance, if you were forwarding mail to Pobox from Gmail, since Gmail is not a spammer domain, those messages would fail all our sending domain checks. If you let us know what address you're forwarding the mail from, we can change your filters so it ignores that sending domain, and instead checks who sent them the message.