This has been  discussed at least a million time...  A very long argument
that leads to a rather simple situation. Either there is a GOOD REASON to
add a "Sender:" field, or it  doesn't really matter and both addresses do
the same and go  to the same person. If it doesn't  really matter then it
shouldn't really  matter whether  LISTSERV uses  "Sender:" or  "From:" to
send its reply. If there was a  GOOD REASON to add a "Sender:" field with
a different address,  then there is the same GOOD  REASON for LISTSERV to
use that  field and not  "From:", otherwise why  insert it? The  catch of
course is that there is a third  option: the case where a "Sender:" field
was inserted  that does  not point  to the same  person, and  where there
isn't  any good  reason for  inserting that  field ("it  looks cute",  "I
didn't read the  RFCs carefully and I  thought my gateway HAD  to do it",
etc). In that  case the gateway should  be changed. I really  have a hard
time understanding people  who make their gateway  put their (postmaster)
address in the "Sender:" field, and  then complain that they actually get
mail as a result.
 
As for  "Reply-To:", LISTSERV does  not use  it to send  command replies.
This is  a design decision,  there are  arguments for both  cases. RFC822
does  not  mandate  the use  of  the  "Reply-To:"  field,  it is  just  a
suggestion. Besides, there  was no automated mail server  when RFC822 was
written.
 
  Eric