To put a little more context to Glenn's post:
There are at least significant processes involved in the processing of
the RFC822 REPLY-TO: field
1) the poster's mail client
2) LISTSERV's use of the list definition keyword * REPLY-TO=
3) the subscriber's particular mail client with multiple REPLY options
The various combinations makes for some unhappy campers when they don't
reply to where they thought they were.
/Pete