spf-discuss
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Re: followup: Re: [spf-discuss] libspf2 sample programs

2007-01-04 15:10:01
UNCLE !!

Ok, I'm convinced.  Now, how to do it.  I'm running SPF (1.999) with Exim 
(4.60-1) (on Sun Solaris 8, Perl, 5.6.1 but I don't think that matters).

In the example acl provided with Mail::SPF::Query, if doesn't even have a 
MAIL command check, but that seemed easy enough to fix:

acl_smtp_mail = acl_check_mail

acl_check_mail:
# Do SPF test
  drop    !acl          = spf_mail_acl
  accept

spf_mail_acl:

    # Check envelope sender

    warn     set acl_m8  = $sender_address
    deny     !acl        = spf_check
    warn     message     = Received-SPF: $acl_m8 ($acl_m7)
    accept

(really the same as spf_rcpt_acl)

but how do I get at the HELO command?  I don't think there is an exim 
acl_smtp_helo acl.

Also, drop vs deny??  I think I would want to drop a connection as soon as 
I know its a spammer, but is there a reason to use deny instead?

Thanks,

Dan



Please respond to spf-discuss(_at_)v2(_dot_)listbox(_dot_)com

To:     spf-discuss(_at_)v2(_dot_)listbox(_dot_)com
cc:      (bcc: Dan Mitton/YD/RWDOE)
Subject:        Re: followup: Re: [spf-discuss] libspf2 sample programs
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User Filed as: Not a Record

(this time with the formatting gink removed - sorry)


What about RFC 1123 where it states:

      5.2.5  HELO Command: RFC-821 Section 3.5

        The sender-SMTP MUST ensure that the <domain> parameter in a
        HELO command is a valid principal host domain name for the
        client host.  As a result, the receiver-SMTP will not have to
        perform MX resolution on this name in order to validate the
        HELO parameter.

        The HELO receiver MAY verify that the HELO parameter really
        corresponds to the IP address of the sender.  However, the
        receiver MUST NOT refuse to accept a message, even if the
        sender's HELO command fails verification.


It is very important to keep e-mail policy separate from e-mail MTA
correctness.  If I violate the above in my MTA, then I may not be
compliant with RFC 1123, and my MTA is not "correct"ly implemented.
However, as an e-mail admin, I have an
absolute right to refuse or accept any mail I want to, on any basis I 
choose.

The MTA is governed by RFC 1123, and it needs to give the admin
the choice of accepting the mail.

SPF is a tool that can be used by the admin to determine which
e-mail to accept based on policy.

-dgl-

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