[dmarc-discuss] MLM and Header-From rewritting - the SMTP open-relay analogy

Dave Crocker dhc at dcrocker.net
Sat Jun 7 02:53:43 PDT 2014

On 6/6/2014 10:59 PM, J. Gomez via dmarc-discuss wrote:
> I cannot stop thinking that the push-back against MLMs rewriting the Header-From is akin to the push-back of about 28 years ago from some people against the move to consider SMTP open-relays harmful.
> Closing SMTP open-relays impedes open and unrestricted email communication, they said, and it was true.

Besides a basic rah-rah emotional tone, the problem with this thread is
that it is both based on an undocumented reference to "they" and some
seriously flawed comparisons.

In spite of seeing the supporting note posted that cited complaints back
when open relays were closed, my own recollection was of mounting
community support.  But that's a matter of history and recollection,
which invites debates about who has the better memory (absent real

More serious are the technical differences between then and now.

First, relays are needed only by their authorized users.  Hence, any
issues with closing an open relay are relevant /only/ to the operator's
own users.  Second, open relays were not /required/ for legitimate users
of the relay.  Port 587 provided/provides an entirely sufficient
alternative.  There is a switching cost, to move to it, of course, but
after that, life proceeds quite comfortably and with no change to the
author/recipient email paradigm.

The current case matches none of these characteristics.

It imposes a meaningful change to the author/recipient paradigm; it has
no clean replacement; and it inflicts collateral damage on innocent
bystanders who are not part of the operator's user base.

Dave Crocker
Brandenburg InternetWorking

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