Re: Setting Reply-To: using exim?

[brian moore <bem@cmc.net>]

On Wed, Feb 07, 2001 at 10:05:13AM +1030, Mark Phillips wrote:
> Sean 'Shaleh' Perry [shaleh@valinux.com] wrote:
> > enable /etc/email-address use.  I use this so that mail from
> > shaleh@mymachine.whereiam.foo becomes shaleh@whatIwant.com.
> 
> I could do this, but I have been told in the past that this is bad.
> Let me explain what I was told.  If my secondary isp thinks of me as
> "markphillips@cheapisp.com.au", but the email address I want to use is
> "mark@infoeng.flinders.edu.au" then as you say I could rewrite
> addresses so that markphillips@cheapisp.com.au becomes
> mark@infoeng.flinders.edu.au.  But then my machine is lying.  It
> pretends to be sending from infoeng.flinders.edu.au when really it is
> sending from cheapisp.com.au.  Apparently the smtp transaction envelop
> will still show the email as originating from cheapisp.com.au.  And
> apparently some mailservers don't like this discrepancy.  If the
> envelope sender is different from the headers sender then it rejects
> the email, causing it to bounce.  And this bouncing has even more
> problems.  It bounces it back to the envelope sender domain.  So
> cheapist.com.au gets the bounced message, but they don't know what to
> do with it, because the "From:" address is one they don't recognise.

Any mail server that did that would be severly broken.  Errors have gone
to the SMTP envelope sender for 20 some years.  The envelope sender
hasn't matched the relayhost for that long, too.  (Think the obvious
case of UUCP mail and the less obvious but amazingly frequent case of
virtual hosts, and the even MORE frequent rewrites from
'user@shellserver2.somehwere.edu' -> 'user@somewhere.edu'.)

Any mail server that compares SMTP envelopes with the domain of prior
mail servers is -broken-.

Any mail server that compares the SMTP envelopes with the 'body From:'
is broken.  (See this very item: where the SMTP envelope will say
debian.org and yet I have no address on any debian server.)

Masquerading has been common for 20 years.  If people are attempting
to detect it in some misguided effort to eliminate spam, they will lose
a lot of mail.

-- 
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