Mailing List Archive

Source routing of email?
OK, I am a Good Guy, I want to *really* use SPF and to replace Bad
"?all" with Nice "-all". I need to be sure that every mail pretending
to come from example.com went indeed through example.com's mail
servers.

When everybody works on-site, this is easy. When people work off-site
and loves ssh and mutt, it is still possible.

Now, some people works off-site and uses Thunderbird or Outlook.

The link on SMTP AUTH in http://dev.spf.pobox.com/whatdoes.html is not
really a HOWTO but I read RFC 2476 "Message Submission", I eat stuff
like http://postfix.state-of-mind.de/patrick.koetter/smtpauth/ or
http://support.earthlink.net/mu/1/psc/img/walkthroughs/Help_FAQ/7280.psc.html
and I feel better after a few nights (SPF deployment is good for
keeping the brain working).

Now, I have some users which work off-site and have an Unix machine at
home (several, actually, but this one if the official home MTA). The
MTA on this machine sends mail with an MAIL FROM example.com but also
nerim.net or bortzmeyer.org.

I would like to route the mail, not according to the destination
(which is trivial with Postfix) but according to the source. Googling
on this issue is a bit depressing because you always find messages
saying "Thou shalt not do this".

Options like (Postfix) :

sender_based_routing (default: no)
This parameter should not be used.

ou like the patch (sendmail) :

+ifdef(`_SENDER_BASED_ROUTING_', `dnl
+R$+ <@ $+ > $:$&f@$j<>$1<@$2> prepend local sender
+R$+@$+@$j<>$+<@$+> $:$1@$2<>$3<@$4> avoid duplicate domain
+R$+@$+<>$+<@$+> $:$(mailertable From:$1@$2 $:@$2$)<>$3<@$4>
+R$*@$+.$+<>$+<@$+> $:$(mailertable From:$2.$3 $@$1 $:$1$2@.$3$)<>$4<@$5>
+R$*@$+<>$+<@$+> $:$(mailertable From:$2 $@$1 $:$)<>$3<@$4>
+R$-:$+<>$+ $@$>MailerToTriple <$1 : $2> $3
+R$*<>$+<$+> $:$2 <$3>
+')dnl ## end _SENDER_BASED_ROUTING_

are a bit frightening.

What are the ways out?

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Re: Source routing of email? [ In reply to ]
On Aug 24, 2004, at 5:40 AM, Stephane Bortzmeyer wrote:

> Now, I have some users which work off-site and have an Unix machine at
> home (several, actually, but this one if the official home MTA). The
> MTA on this machine sends mail with an MAIL FROM example.com but also
> nerim.net or bortzmeyer.org.

Do the hosts running those MTAs have static IP addresses? If so, just
add them to the SPF records. If not (as I guess is the case) then you
do have the problem you describe below:

> I would like to route the mail, not according to the destination
> (which is trivial with Postfix) but according to the source.

Hmm. I only have a passing familiarity with postfix, so I can't
answer. I am confident that this would be easy to do with exim, but
even then I couldn't say off of the top of my head how to do this.

MUAs, of course, have the nice concept of roles, where one does exactly
this. But if MTAs (or Postfix as needed in the specific case) doesn't,
I can only suggest unclean work-arounds which you've probably alreay
thought of.

Would there be a problem with example.com handling some of nerim.net's
and bortzmeyer.org out-going mail? Presumably those are vanity domains
of people closely associated with example.com.

Beyond that, all I can do is recommend that you ask on Postfix lists.
Sorry I can't be of more help.

-j

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