Re: [Exim] why was this rbl checked?

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Author: dman
Date:  
To: exim-users
Subject: Re: [Exim] why was this rbl checked?
On Fri, Apr 12, 2002 at 09:29:42AM +0100, Philip Hazel wrote:
| On Thu, 11 Apr 2002, dman wrote:

|
| > hostlist not_rbl_hosts = <, !192.168.0.0/23 , !127.0.0.1/32 , !::1
| >
| >     warn    hosts = +not_rbl_hosts : !129.21.30.24
| >             dnslists =  \
| >                     dsn.rfc-ignorant.org/$sender_address_domain : \
| >                     postmaster.rfc-ignorant.org/$sender_address_domain : \
| >                     abuse.rfc-ignorant.org/$sender_address_domain
| >             message = X-RBL-Warning: $sender_address_domain , $dnslist_domain , $dnslist_value , $dnslist_text
| >             log_message = RBL : $sender_address_domain , $dnslist_domain , $dnslist_value , $dnslist_text
| >
| >
| > I got this in my rejectlog :
| >
| > 2002-04-11 19:07:44 H=(martha.itusa.org) [192.168.0.4] Warning: RBL : 192.168.0.4 , abuse.rfc-ignorant.org , 127.0.0.4 , Not supporting abuse@domain

|
| > My understanding is that that message shouldn't have been checked at
| > all because it came from 192.168.0.4 (the internal side of that host).
| > As it was, the domain in the Reply-To: is what failed the test.
| >
| > Why was this message checked?

|
| You have fallen into a trap/confusion. Unfortunately, the flexibility of
| all of this introduces complications that aren't always easy to check
| out. The interactions between negations and named host lists don't
| always work the way people expect.

|
| Your case works like this:

|
|   . Exim sees "+not_rbl_hosts", so goes away to check if the host
|     matches that named list.

|
|   . 192.168.0.0/23 does match 192.168.0.4, so the answer is "no, it
|     doesn't match +not_rbl_hosts".


|     (Your name is a bit confusing. It should surely be "rbl_hosts",
|     shouldn't it?)


It was named that, but when I went through the config again it seemed
to be the opposite of what it is intended to be. It is supposed to be
a list of hosts that are not to be checked against any rbls. "rbl
hosts" sounds, to me at least, like something that would be rbled.

|   . So Exim proceeds to look at the rest of its list. The host doesn't
|     match 129.21.30.24, and that's the end of the list.

|
|   . When a list ends with a negative item, there's an implied :* at the
|     end, so the host matches.


Ok, that does make sense.

| It is a general case, in English and in logic, that dealing with
| negatives is confusing, and double negatives are doubly confusing.


You are right. That's why I didn't really like "negative logic" when
I took Intro to Digital Systems. It was all "backwards".

| Try
| writing it like this instead:

|
| hostlist local_hosts = <, 192.168.0.0/23 , 127.0.0.1/32 , ::1

|
|   warn    hosts = !+local_hosts : !129.21.30.24


I've done this, except I'm keeping the name since I think it conveys
the purpose better. Hmm, maybe "skip_rbl_hosts" would be an even
better name.

| Named host lists are not the same as macros. They are like subroutines.
| What you wrote would work as a macro, because the address would then be
| "not in the host list" instead of just "not in this item of the host
| list".


Funny, since I've never used macros in exim. I'm not sure if
convert4r4 created it like that or if I adapted an example from
somewhere or just goofed it up myself, but the extra '!129.21.30.24'
wasn't in it at that time, so I think it was actually working properly
before I added that.

Thanks!
-D

--

Microsoft encrypts your Windows NT password when stored on a Windows CE
device. But if you look carefully at their encryption algorithm, they
simply XOR the password with "susageP", Pegasus spelled backwards.
Pegasus is the code name of Windows CE. This is so pathetic it's
staggering.

http://www.cegadgets.com/artsusageP.htm