A few daysago I have answered to the same question, because I 've had this problem too. But I've had luck and found a solution, which works on my Win-PC, and as I received feedback on other machines too:
I'd coppied the NPOJI600.dll into the plugin-folder of mozilla. This .dll I did get from a testinstallation of Netscape6.2. After doing this, I was happy to see, that my java machine works. I hope, it helps. Mmmh, but I don't understand the context to this 'mozilla.mail-news'. Gru� Wolf
