That longer address works (wrote to it several times today), though I wish WGT would make the switch to the short email address already (it's a matter of seconds to set up the redirect); they've been the owners of the wgt.com domain for many months now.
Could be a problem with the poczta.pl SMTP server; I must say I've had bad experiences with it myself when I tried to communicate with some of my Polish colleagues. They had to switch from Poczta.pl to Gmail in order to be able to communicate with the rest of us (outside of Poland) normally; Poczta.pl (a freemailer) kept deleting legitimate incoming email, etc.
PS: Oops, the quotations from email headers messed up this forum page's design.