Re: Forged sender test

["Alexey Lobanov" <aal@evidence-cpr.com>]

Hi Vince,

On 11 Jan 2003 at 14:49, Vince Puzzella wrote:

> > Just note that you will reject a lot of legitimate mail.

> I am aware of the potential pitfalls of such a test.  I was just wondering
> if it is at all possible.

Everything is possible in open-source world, just "man vi" :-). Maybe, those 
"pitfails" just explan why this idea is still not present in standard MTA. Do 
you really want to reject mail from Yahoo (REAL Yahoo, not forged)? 
"...client=mta423.mail.yahoo.com[216.136.129.78]..."

For comparison, examples of real client tests (Postfix MTA):

1. HELO name must be present in DNS as valid A or MX RR.
2. Reverse DNS must exist, including "paranoid check" IP->PTR->A.

In my knowledge, all "well-maintained" mail systems satisfy those two tests, 
and most (really most!) of garbage sources don't.

Alexey


> On 11 Jan 2003 at 9:52, Vince Puzzella wrote:
> 
> From:           	"Vince Puzzella" <vpuzzella@bluecatnetworks.com>
> To:             	<zmailer@nic.funet.fi>
> Subject:        	Re: Router file naming convention
> Date sent:      	Sat, 11 Jan 2003 09:52:08 -0500
> 
> > Is there anyway to get the zmailer smtp server to test for forged sender
> > addresses at the MAIL FROM:<> phase?
> > Essentially, I want to perform a DNS MX record query to verify that  the
> > source IP is a valid mail exchanger for the sender's domain.
> 
> 
> 
> 
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