After mailing my response, I received a number of bounce messages from
accounts that have been deactivated, but also that I suspect should never
have been subscribed to this mailing list.

(one responded asking me to confirm an order, another complaining that I
was sending incorrectly formatted commands)

I don't know what mechanisms yahoogroups has for maintaining a clean
mailing list, but it might be time to cull the list to deal with 'problem'
accounts subscribed to it.

-----
Joe Hourcle