Thanks for posting your question here.
If you would like to exclude shipping to PO box addresses when listing through Auctiva, just check the radio button next to “Select locations to exclude” in the “Shipping Tools” area and check the box next to “PO Box” on the ensuing list.
On a related note, you could also potentially create an exclusion list within your eBay account that indicates you will not ship to PO box (and potentially other) locations, and then use that entire exclusion list when posting your items through Auctiva by checking the “Use my eBay shipping exclusion list “ option.
You should be able to create (or edit) your shipping exclusion list within your eBay account by going to your “My eBay” page, selecting “Site Preferences” from under the “Account” tab, clicking the “Show” link next to “Postage Preferences”, clicking “Edit” next to “Exclude postage locations from your listings” and the proceeding as directed.
I hope this helps. If you need any more specific assistance with this, please feel free to contact our Customer Support team directly from under the “Help” tab on our site and we will be happy to continue working with you.