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

2007-01-04 15:19:37
Ok, maybe is will not be too hard.  Looking at the online Exim 
documentation, it looks like there IS a acl_smtp_helo acl.  In the book I 
have, from 2003, there is not.



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


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

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(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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