The problem has been resolved.
Seems there was a congestion prob that was leading softhome to blackhole anything outbound to yahoogroups. This was the cause of the mail looking like it was directed to RFC1918 space.

After some discussion with people on both ends, a workout was achieved.
Doug, Brian, hats off...thanks. I know you're reading this somewhere.

I personally want to thank the people, too numerous to cite individually who got both softhome and yahoo net people into the loop. I know there were more than a few nanogers involved, things just don't go this smooth otherwise. You people are like firefighters, unappreciated until we need you.
The reports I got from you all were informative and helped us bring this to a successful and rapid conclusion. A lot of people who have no idea how the net functions are sending mail again, without knowing there was even a problem.
I'm usually cited here as more a PITA than a contributor here, but I do give credit where due, thanks to you all, from the traceroutes, and digs, and the prodding and private emails (All appreciated).

I'm not much for patting the backs, but you people here are the best. My problem was insignificant compared to the daily grief you folks deal with and the bandwidths you manage.

I'm proud to associate with you, and extend my thanks.

Now you all go have a good, un-interrupted holiday.....may the pagers and C-phones be silent, and the emails be few.

Marc Blitz