Re: Use of Sender in authentication considered unacceptable (was Re: draft-lilly-from-optional-01.txt)

>> If you want a viable authentication proposal, you need to define a new
>> field which will have a well-established meaning, not try to borrow 
>> some
>> existing field which has either a different meaning (From) or some
>> existing field which has no consistent use in practice (Sender).
>
> I agree that we don't see a consistent use of the Sender field in 
> practice.  If the agent responsible for the transmission of the 
> message makes proper use of the Sender field, I don't see why we 
> should redefine a new field when there is already a field which was 
> set out for that purpose.

because in practice Sender is almost never used properly, and use of 
Sender is so varied that the recipient cannot tell what is meant by it.

for example: mailing lists should almost never set Sender, because it 
obscures who actually sent the message, and this is of interest to list 
recipients.  (there are exceptions: it's reasonable for digests to set 
Sender to point to the mailing list.  similarly for lists that 
deliberately try to hide the actual addresses of the correspondents)

Keith