Wayne, that's good. I wasn't expecting it to be anything like that.
Open relays are just part of the spam problem.
Basically what the spammers are after are email addresses, once they get them, they're gone. They will remain in the spammer databases forever.
So, basically, trying to "hide" your email addresses from spammers will not work in the long run.
The real solution is to install some good spam filter program (either locally, or to receiving email server). In this case amiga.org could run spamassassin, I think. This way 95-99% of spam would stop at amiga.org and would not be relayed to final recipients.