VERY DISAPPOINTED - parcel arrived open and incomplete, with no grounds to do so

I have sent from South Africa to Poland 43 closed envelopes with wedding invitations. There was no money or anything what would be forbidden to ship. The invitations themselves cost me R 2200 (including special glittering envelopes) + shipment R 1 825 - and I specifically took a larger box, that cost about R600 more, to be sure that invitations arrive in the same perfect state as sent. I was extremelly unhappy when I learned that about 10 envelopes were opened. As I stated before, there was no money inside and I believe there were no grounds to open the envelopes, as they could be easily scanned to make sure there is nothing else inside. When claimed, DHL responded that it's within the limited liability.