Hi philliman, good questions

You're right, this has been asked and answered several times already but it's probably easier to simply restate the answer.
You can mask your own IP address, as you rightly state you simply use an anonymous proxy and your own IP address will be masked - the IP that shows up on email headers, server logs etc. will be the IP address of the proxy server.
What Ivo is doing, and he knows he is doing this because no one can be that stupid so many years after the fact, is using the "easy" definition of IP masking (above) and applying that to something else entirely, namely changing your IP address to match that of someone else - a
completely different thing altogether!
Mask your IP address? easy.
Change your IP address to match an existing IP already on the network? are you kidding me?
Incidentally, this was exactly the excuse used by Kit Green when we exposed Doty in the first place.
"It's easy to change your IP address, it's easy to pretend to be someone else".
I repeatedly told them to prove it, right there and then. If it was so easy, how come they couldn't reproduce the effect when asked?
"It's easy!" "Do it then!" "But it's easy!" "THEN SHOW ME!" In the end, Green conceded the point (months later) and admitted he had been "misled". Yeah, right. And now Iversen is parroting the cat...
There are methods you can use to try and fool people though, but these will always end up being apparent with the minimum of effort. I once, by way of example of what was easy and what wasn't, sent out a number of emails that appeared to come direct from DIA servers. It was enough to fool the usual suspects, with a complicated route through various military email servers, but I added all of that information myself, at the server end. I changed the server name to match a particular DIA mail server but of course the IP address didn't match. All of the (added) headers after that did match, but the original, originating IP address? That was the public IP address of my network.
What Iversen is suggesting is absolute poppycock. There are so many things wrong with his statement I don't really know where to begin. A trawl through the various threads will probably help me there

The main area where Iversen's explanation falls down, aside from the obvious technological reasons (more on that below), is that Bill Ryan had already admitted he was getting his information from Rick Doty!
I really should finish the Serpo Uncovered (
http://www.realityuncovered.net/ufology/articles/serpo/) section, answering questions like this would be so much easier.
The link above explains some of it, but also these pages at the old .com site will help, which once rewritten will form much of the Serpo Uncovered content mentioned above:
http://www.realityuncovered.com/expose.shtmlFollow the links at the bottom of each page and it all should become clearer. Essentially, Doty screwed up and thought he was using a webmail provider (Lycos) that masked your IP address. It didn't.
Now, why would Iversen continue to ignore the facts and the evidence wrt Serpo?
S'ok, I already know the answer.
Cheers,
Steve