[Mimedefang] Return-Path help

Jan-Pieter Cornet johnpc at xs4all.nl
Fri Dec 15 11:23:30 EST 2006


On Fri, Dec 15, 2006 at 10:20:50AM -0500, David F. Skoll wrote:
> >   ----- The following addresses had permanent fatal errors -----
> > <someuser at domain.com>
> >    (reason: 556 Mail from nullsender not allowed (#5.7.1))
> 
> That machine is broken.  See http://www.rfc-ignorant.org/policy-dsn.php

Indeed. Note, however, that this is usually done because the user
is being joejobbed. In fact, you are doing him a service sending
vacation message as a "bounce", because the vacation could have
been triggered by the joejob too, so it is then (rightfully)
being ignored.

Also: lots of _other_ sites are doing sender verification, by
connecting back to the mailserver of the (claimed) sender, and doing
MAIL From:<> RCPT To:<purported.sender at domain>.

Now, the merit of this check is a whole debate in and of itself,
but the fact is that it exists. Those users are going to find they
cannot email to those sites. Most likely, the email just magically
disappears (because it gets rejected for a sender callout verification
failure, bounces, and then the bounce itself is rejected by the
null sender blocking).

I'd just ignore this issue, if I were you. The above someuser at domain.com
has problems enough already.

> Basically, machines that reject mail from <> are ignorant of the RFCs
> and deserve to be blacklisted.  I would file a bug report with
> postmaster at domain.com and abuse at domain.com, pointing them to the
> rfc-ignorant.org site.

Hmm, David, since when did you change your opinion on rfc-ignorant? :)

> > I can't figure out how to make sieve add the correct name in the return
> > path, so is there a way to make Mimedefang do it on the way out?
> 
> Not easily, at least until Sendmail 8.14 is out.  It will allow milters
> to change the envelope sender (not that MIMEDefang supports that yet!)

It can be done with mimedefang, just not very easy. In fact, it's ugly.
You'll have to tell sendmail to discard the message, and then resubmit
it to sendmail with another envelope sender.

-- 
Jan-Pieter Cornet <johnpc at xs4all.nl>
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