Re: [Asrg] Re: SPF abused by spammers

Markus Stumpf wrote:

> On Fri, Sep 17, 2004 at 03:11:18PM +0000, Mark wrote:
> > Hello? Ever heard of HELO? :) Sending with en empty envelope-from,
> > to try and circumvent SPF, is pointless: checks are done against
> > HELO, in that case (as if tested against, say, postmaster(_at_)HELO).
> > Consequently, since there is nothing to prevent, there is nothing to
> > send "non empty" either (where empty was the case).
> That was the reference I didn't find.
>
> Which leads to the problem with
>
>   HELO [10.0.0.1]
> or
>   HELO i222-150-67-241.s04.a013.ap.plala.or.jp
>
> which would require all ISPs to add SPF records to all entities and
> raises again the problems Barry Shein has addressed.
Well, only if that ISP allows people to send mail from their home IP 
addresses. Otherwise, the ISP just has to create SPF records for its own 
outgoing mail servers.
If people on a home network get their own $9 bucks domain name, they could 
(and probably should) set their HELO string to their domain name, if they 
are also sending from their home IP address(es). Then they can, themselves, 
publish, or have published, SPF records for that domain. Setting HELO to 
their PTR (if unchangeable, and provided by the ISP, and in the above format 
you described), would not make much sense, in that case.
> And: if I am a customer of some.isp and my current revDNS entry for
> the IP I am using is
>
>    1.0.0.10.rev.dsl.some.isp
>
> should I be allowed to send a bounce on behalf of that address, i.e.
> use the name or IP in the HELO string?
I doubt you'll get far with a 10.0.0.1 address. :) But, assuming a public 
address, why should you not be allowed to send a bounce from that address? 
SPF "classic" does not check against your PTR; so, if you have proper SPF 
records for your domain/HELO, why not? If your HELO is set to your own 
domain name, and an A record lookup of the HELO matches your IP address, 
you're in the clear.
- Mark


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