ietf-mxcomp
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Re: Benefits/costs of authorizing different identities

2004-04-05 10:05:24

Folks,

It appears that there is good focus on the SMTP-level identities, so
I'll leave out discussion of the message-level identities.

By and large, the discussion has focused on benefits, but not costs.

There is massive abuse of MTA.MailFrom addresses, and that that abuse
is extremely damaging. By contrast, any abuse of MTA.Helo is not very
problematic.

So the direct benefit of focusing on MTA.MailFrom is quite obvious.

Unfortunately, MTA.MailFrom is a value set by the Msg.Sender.  It is
therefore a derived value, from a very different functional component
of the service.  And we know that validating Msg.Sender has some
challenges.

The proposals for directly validating MTA.MailFrom have a serious
impact on valid email scenarios that are already in use. They are
likely to damage core email utility is very basic ways, both in terms
of basic functionality and in terms of administrative overhead.

The value in focusing on MTA.Helo is that the field is localized
between the peer MTAs and validating that field provides an
incremental basis for stable, trusted Internet mail infrastructure
operation.  The charter for this group is on peer validation.

Small increments of improvement are not very sexy. However the lack of
real success at reducing the global level of email-based attacks
should make us all cautious about direct solutions on indirect
portions of the service (like MTA.MailFrom).


d/
--
 Dave Crocker <mailto:dcrocker(_at_)brandenburg(_dot_)com>
 Brandenburg InternetWorking <http://www.brandenburg.com>
 Sunnyvale, CA  USA <tel:+1.408.246.8253>, <fax:+1.866.358.5301>