To separate your messages based on the address it was sent to, just change the forwarding for that address. Delivery by alias (delivery groups) is available for all Pobox Plus and Mailstore accounts. So, if you have access to filters, you have access to delivery groups, and delivery groups are a much more reliable way to make sure messages go to the right place based on the To: address it was sent to.
Using email filters to separate your mail based on address is not recommended, ever. Email filters have to run in order, and they stop processing filters as soon as the first one matches. So, messages sent individually to an address would be delivered properly. But, if a message is CCed to two addresses on your account, and you used email filters to separate them, then one address would get two copies of the message, and the other address would get none. Delivery groups were added to avoid that problem.