In Poland, the biggest local mailbox providers are (if my memory serves me right -- it has been a few years) Wirtualna Polska, Onet, Interia and UPC Polska. Wirtualna Polska, which covers the domains wp.pl, o2.pl, tlen.pl, go2.pl, and 10g.pl, has long advertised a "Premium Sender" service where those sending significant volumes of bulk mail must register and pay to be able to get t…
