When you get the error message [TS50: Recipient address is a PO box, carrier can not deliver to a PO box.] this means that the address used (postal code in combination with house number) is a PO Box delivery address. Eventhough the error message is sent by Transsmart, the allowance to deliver to this type of address is determined by the carrier used. 

Please check the combination used. It is possible to validate addresses online via Google maps or any other address validation website.

For some carriers it might be allowed to deliver to a PO box address, please check this with your carrier first.

If you are certain that the address is not a PO Box, please contact us through this link to investigate this further.

Take into account that there might be consultancy costs involved.