On Thu, 24 Mar 2005, Marilyn Davis wrote:
> On Thu, 24 Mar 2005, Marc Sherman wrote:
>
> > Marilyn Davis wrote:
> > >>
> > >>>But then, can't we use bounce_message_file to customize the message
> > >>>so that it is as friendly as a regular challenge?
> > >>
> > >>No, because if you're responding with a 5xx to reject the message, you
> > >>don't generate any bounce; the _only_ text you get to specify is in the
> > >>5xx reason string. If a bounce is generated, it will be generated by
> > >>the originating MTA.
> >
> > Just to follow up on this, I've been experimenting with my own spam
> > rejection system today, and discovered that at least Exchange severely
> > limits the size of the text it will display in a bounce caused by a 550:
> >
> > > The following recipient(s) could not be reached:
> > >
> > > msherman@??? on 3/24/2005 1:47 PM
> > >
> > > There was a SMTP communication problem with the recipient's email
> > > server. Please contact your system administrator.
> > >
> > > <to-exchsrv-01.fortiva.corp #5.5.0 smtp;550-Spam score too high
> > > (996.8). Contact postmaster@??? for>
> >
> > The error message I sent back ended with " assistance." but that was too
> > long. So if you try to implement a c/r system using 550 responses to
> > send the challenge, the url to respond to the challenge had better be
> > pretty small.
>
> Wow. Bummer.
>
> Thank you for the report.
I did another experiment -- trying to duplicate yours, using my friend
Mike, who says he's behind MS Exchange.
On my test domain, running exim 2.50, I did this:
acl_check_sender:
deny message = "Hi Michael. xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
condition = ${if eq{$sender_address}{mike@???}{yes}{no}}
On this, my production machine, running exim, I did:
exim -f mike@??? marilyn@??? < /some/file
And he, poor sucker, gets the error message:
2005-03-24 14:17:22 1DEadm-0004X5-Qq <= mike@??? U=root P=local S=1759
2005-03-24 14:17:22 1DEadm-0004X5-Qq ** marilyn@??? R=dnslookup T=remote_smtp: SMTP error from remote mailer after MAIL FROM:<mike@???> SIZE=2826: host al.test.machine [10.0.0.153]: 550 "Hi Michael. xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
2005-03-24 14:17:23 1DEadm-0004XA-Vj <= <> R=1DEadm-0004X5-Qq U=exim P=local S=3356
2005-03-24 14:17:23 1DEadm-0004X5-Qq Completed
2005-03-24 14:17:28 1DEadm-0004XA-Vj => mike@??? R=dnslookup T=remote_smtp H=ext-mx02.hisplace.com [66.134.75.55]
2005-03-24 14:17:28 1DEadm-0004XA-Vj Completed
----
So now I'm wondering, how is this collateral spam from an error better
than the collateral spam from a challenge?
Marilyn
