John Leslie wrote:
Doug Otis and I have been working up a proposal for a SMTP extension
to shift some of the burden of spam abatement away from the receiving
SMTP servers towards the originator. It is now published at:
In essence it holds the originator responsible for maintaining the
copy of the message until a receiving Mail User Agent determines that
it should be delivered to the recipient.
But what incentives do spammers have to use this extension? As long
as normal SMTP exists, I doubt that this will do anything to reduce
spam unless we somehow punish senders who do *not* use the extension.
And that, IMO, is not a good idea.
Additionally, it's difficult for the server holding the message body
to know when it's safe to delete it. Let's say a message is sent
to 100 recipients in 37 different domains. Should the message body
be deleted only after 100 attempts to download it? 37 attempts? Some
other number? There is no way I can see to give feedback to the server
that "Yes, I take responsibility for delivering this message to recipients
X, Y and Z (but not P, Q and R.)"
Making trace headers optional is asking for trouble. It makes
diagnosing mail problems nightmarish.
If a TBR message is not fetched, how long should the server hang on to it?
Suppose you're AOL or Hotmail and in the business of sending several billion
e-mails per day... what implications does implementing TBR have on your
This looks more-or-less like a reinvention of http://cr.yp.to/im2000.html
and will probably meet with the same level of enthusiasm.