Received: from localhost by CS.UTK.EDU with SMTP (cf v2.9s-UTK)
	id WAA20826; Tue, 3 Oct 1995 22:25:59 -0400
Received: from CU.NIH.GOV by CS.UTK.EDU with SMTP (cf v2.9s-UTK)
	id WAA20817; Tue, 3 Oct 1995 22:25:55 -0400
Message-Id: <199510040225.WAA20817@CS.UTK.EDU>
To: drums@CS.UTK.EDU
From: "Roger Fajman" <RAF@CU.NIH.GOV>
Date:     Tue, 03 Oct 1995  22:23:01 EDT
Subject:  Re:  What's the Sender header for?

It may be helpful to try to list the uses to which the Sender header is
currently put.  Here's the ones that I can think of:

(1) Some mailing list software uses Sender for the name of the list or
the list-request mailbox.  This has the utility of answering the
question "why did I receive this message".  The To header may not be
sufficient for that since it may contain multiple list addresses.
LISTSERV is not the only MLM that uses Sender.  Listproc puts the
listname-request address into Sender.

(2) Some user agents allow the user to sent the From field to whatever
they want.  This is useful when the address that one wishes people to
use is one that goes through a forwarder (e.g., fajman@nih.gov). The
utility of the Sender field in this context is that is can be used to
indicate where the message really came from, so as to discourage
forgery.

I rarely see this usage.  One of the more popular user agents that
permits the From field to be set by the user is Eudora.  We use Eudora
a lot here and, at least as normally configured here, it does not put
in a Sender header.  Probably it does not know what it should put into
one.

(3) A secretary might be sending mail on behalf of a boss.  In this
case, the boss's address should go into From, and the secretary's
address into Sender.  I don't know of a UA that makes this easy to do,
but there must be something that does.  I rarely see it, however.

What else is there?

Roger