On Wed, 2004-12-15 at 11:41, Dave Crocker wrote:
On Wed, 15 Dec 2004 11:11:38 -0800, Douglas Otis wrote:
Although the MAILFROM is set by the Submitter, it represents the
return-path.
Not really. It represents the bounce address.
I should have said for a message bounce. : )
There is no requirement that it have anything at all with reaching any
of the folks involved in creating or sending the message. In fact,
there are legitimate scenarios that set it to an entirely different
address, in order to separate bounce processing.
Current use of MAILFROM allows retaining this field to
avoid establishing a mailbox to handle returns. The HELO is closely
tied to host and thus is not as flexible as the Sender header, which is
also set by the Submitter.
HELO is quite flexible. It is set per session. In fact, it can be
re-set during a connection, to establish a new session.
What is distinctive about HELO is that it identifies an operator of
the MTA rather than anything about particular messages.
This legacy seems to constrain how HELO would be used with respect to
signatures by the Submitter, as there is less support allowing this
field to be dynamic. It would also tend to involve a greater level of
administration relating to the host. Yes, HELO could work for this
function. Which do you think would make more sense however-
HELO or Sender?
-Doug