On Friday 21 February 2003 20:26, Chris Bayliss wrote:
> On Fri, Feb 21, 2003 at 01:06:35PM -0500, Owen Creger wrote:
> > Exim 3.12
> > Spammer sends an email to a non-existant account.
> > Exim relay dutifully passes it to our internal mail server
> > Internal server rejects message, recipient unknown, and passes it back
> > to the Exim relay.
> > Since reply-to address is forged, Exim has no way to route/send unknow
> > recipient message back to spammer.
> >
> > Exim wasn't compiled with LDAP in it, so I can't verify addresses from
> > the relay. Plus I understand LDAP querys are more of an art than
> > science.
> >
> > Can I modify my routers/directors to throw out the unknown recipient
> > messages coming from my internal server?
A better approach may be to go after the cause of the problem, rather than
the symptom. Is your server checking black lists, and have you installed
spam filters?
You should be able to install them on the external relay. In doing so, the
message will be checked before it is checked for recipient validity, and
thus, most spam will never get to the point where it causes this problem.
>
> It depends on whether you want a reliable mail service or not. If you
> throw out unknown recipient messages you won't have one. Consider the
> genuine sender who mis-types an address. If you throw out the unknown
> recipient message they'll never know that their message wasn't delivered.
>
> There is no reliable means of telling for certain when an address has
> been forged. It just has to be accepted that in some circumstances
> you will deliver an error message to an innocent victim.
>
> --
>
> ## List details at http://www.exim.org/mailman/listinfo/exim-users Exim
> details at http://www.exim.org/ ##
--
Willie Viljoen
Freelance IT Consultant
214 Paul Kruger Avenue, Universitas
Bloemfontein
9321
South Africa
+27 51 522 15 60
+27 51 522 44 36 (after hours)
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