From: Alex van den Bogaerdt (alexergens.op.het.net)
Date: Fri Mar 12 2004 - 08:22:36 CST

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On Fri, Mar 12, 2004 at 09:15:00AM -0500, Robert Fitzpatrick wrote:
> On Thu, 2004-03-11 at 21:33, Pedro Fernandes Macedo wrote:
> > I've set up postfix on the main servers in my network with several
> > anti-UCE configurations.
> > However , I still get a lot of spam. The analisys of the logs show that
> > they use my domain in the helo part, so I want to block all the incoming
> > mail (except from mynetworks) using "helo mydomain". Is this possible?
> >
>
> You may also want to check a new emerging standard called SPF. You can
> use SPF records in DNS to stop this type of thing. There is an excellent
> article about it in the Linxu Journal this month.

SPF may not be the tool for this. SPF allows the receiver to check the
validity of "mail from" and "helo". However, if the receiver is the owner
of the domain being questioned (and it is!), SPF is not needed at all.
A simple regexp table is working just as well without the additional
problems that DNS could cause.

SPF does not stop the remote end from trying to send. It allows the
local end to query the remote domain name being used. In this example,
the domain name is not remote, it is local. SPF _will_ work, it is just
not efficient.

cheers,
Alex
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