[spf-discuss] Re: How does one distinguish between authorizing MAIL FROM

> > > > > "Alex" == Alex van den Bogaerdt
> > > > > "Re: Re: How does one distinguish between authorizing MAIL FROM and HELO"
> > > > >  Mon, 29 Jan 2007 16:58:24 +0100
    Alex> On Mon, Jan 29, 2007 at 10:33:01AM -0500, John A. Martin
    Alex> wrote:
    >> I'm afraid again I was unclear or confused.  The question is
    >> for a setup where the MAIL FROM uses a collective domain as in
    >> <local-part(_at_)example(_dot_)com> and the outgoing SMTP relays use 
their
    >> FQDNs in their HELO commands.  To simplify, assume a single
    >> outbound relay and
    >>
    >>>>         example.com.        TXT "v=spf1 ip4:192.168.0.1 -all"
    >>>>         host1.example.com.  TXT "v=spf1 ip4:192.168.0.1 -all"

    Alex> A connection from the host with address 192.168.0.1:

    Alex> SMTP session: HELO host1.example.com SPF:
    Alex> - fetch the record at host1.example.com
    Alex> - result: "v=spf1 ip4:192.168.0.1 -all"
    Alex> - compare: "ip4:192.168.0.1" against 192.168.0.1 -> MATCH
    Alex> - use prefix "+" (implicit here)
    Alex> - return PASS

[...]

    Alex> Host with name "example.com" is the only one authorized to
    Alex> say "HELO example.com".  However, all other hosts on that
    Alex> network should be authorized to say "MAIL
    Alex> FROM:<(_dot_)(_dot_)(_dot_)(_at_)example(_dot_)com>", that's why the 
entire subnet is
    Alex> authorized to use domain name "example.com".

    Alex> Host with name "mail2.example.com" is the only one
    Alex> authorized to say "HELO mail2.example.com".  No other host
    Alex> needs to use this domain name so that's why the SPF record
    Alex> for domain "mail2.example.com" only needs to authorize IP
    Alex> address 192.168.0.2

Exactly what is wanted and what is gotten!

Your nicely laid out examples showed me immediately where I was mixed
up.  Thank you very much for your patience setting it out so clearly.
Next time I am confused, maybe laying out the scenario as you have
illustrated will save everybody some time and myself more than a
little embarrassment.

        jam

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