Subject: Re: Mail sent to midcom (fwd)

From: Keith Moore <[email-masked]>
Date: Thu, 01 Feb 2001 16:08:08 -0500

>     There's another subtlety here - lists that filter mail from
>     non-subscribers penalize folks who use subaddressing for incoming
>     list mail, since they don't post from the same address at which they
>     are subscribed.  Ideally, lists should not consider subaddresses
>     when comparing a contributor's address against the list of
>     subscribers.  Failing that, it's helpful if a subscriber can get his
>     "From" address registered as one for which there is special
>     permission to post.
> 
> Your suggestion to "not consider subaddresses" is impractical at best,
> and illegal regardless.

On the contrary, it's clearly practical as I have running code in 
bulk_mailer that does this (which will be in the next release).  

Nor is it illegal.  Since there are no standards regarding list filtering, 
there are no standards that prohibit lists from doing filtering using 
fuzzy matching rather than exact matching on an address.  My guess is that 
most lists that filter on source address are already taking liberties
when comparing addresses - they're doing case-insensitive comparisons 
of the local-part when according to the standards the local-part is
allowed to be case-sensitive.

It doesn't take rocket science for the list to seperately compare
the domain of an email address and the portions of the local-parts
up to but  not including any of the separators commonly used:
( + - / . =  # )
 
> hosting the elist.  Even if it did you're suggesting the elist server
> should peek or otherwise parse the localpart of an non-local email
> address and that is wrong.

Guess we'd better put a stop to those case-insensitive comparisons, then.

> The only practical solution is, as you propose, that the elist needs to
> have a separate list of addresses approved to submit messages.  

Actually I've demonstrated that there is another practical solution, one
which is unlikely to penalize those using subaddresses at all.

Keith

---

From: Michael Richardson <[email-masked]>
Date: Thu, 01 Feb 2001 17:57:56 -0500

>>>>> "Keith" == Keith Moore <[email-masked]> writes:
    Keith> On the contrary, it's clearly practical as I have running code in 
    Keith> bulk_mailer that does this (which will be in the next release).  

    Keith> Nor is it illegal.  Since there are no standards regarding list filtering, 

    >> have a separate list of addresses approved to submit messages.  

    Keith> Actually I've demonstrated that there is another practical solution, one
    Keith> which is unlikely to penalize those using subaddresses at all.

  Frankly, both are useful and they are complementary.
  
  I run many lists. They are now all restrict_post, but I always make
a corresponding -nomail list. Both are managed by majordomo, but -nomail
has defunct aliases. 

  [email-masked] is like this, and receives daily posts
from people reporting problems. I have a script that subscribes them to
the -nomail list, and then reposts their message. People who post once
usually post a second time.

  It's a lot less hassle than spamming several hundred people, and then
dealing with the "why is that spam there..." etc.
  
  If this is too strong medecine for the IETF, then a system of
"+censored" lists would help.

   :!mcr!:            |  Solidum Systems Corporation, http://www.solidum.com
   Michael Richardson |For a better connected world,where data flows faster<tm>
 Personal: http://www.sandelman.ottawa.on.ca/People/Michael_Richardson/Bio.html
	mailto:[email-masked]	mailto:[email-masked]

---

From: Keith Moore <[email-masked]>
Date: Thu, 01 Feb 2001 20:03:01 -0500

> from people reporting problems.

if the list is set up right, people don't have to report such problems.    
the suspect messages go to the moderator; the moderator either approves
them or not based on whether they're on topic for the list.  if they
are, the moderator can add the poster's address to the list of those
who can post withut moderation.

adding support for recognizing subaddresses just optimizes this
process - the moderator doesn't have to deal with quite so many
messages, and the posters who are using subaddresses don't have
even their first message delayed.  

the system works fine either with our without the optimization.
but it would be nice if mailing lists weren't hostile to those 
using subaddresses.

Ketih

---

From: James M Galvin <[email-masked]>
Date: Fri, 02 Feb 2001 10:12:31 -0500 (EST)

I'm going to stick with my opinion and "agree to disagree" because
although everything you say may be true, my experience suggests
otherwise.  The issue is that of false positives.

I used to do what you describe but the algorithm got it wrong once, or
at least one time that was brought to my attention.  Not because the
algorithm was buggy but because assuming "." is a separator between pure
localpart and subaddress is wrong.  I also had some strange experiences
with "/" in "X.400" addresses, but that may be moot today.  The downside
of getting it wrong may only be annoying, in general, but as a service
provider I can not afford to be annoying.

In my opinion it does take rocket science because you're making semantic
assumptions with no foundation whatsoever.

I called it illegal because a localpart should be opaque outside its
local environment.  I tried to find a reference to this effect in some
standard but couldn't.  It may just be "practiced wisdom" but I can not
remember a time when it wasn't true.

You more or less got me on the case sensitivity issue.  I also agree
with your assessment that most filtering practices incorrectly do case
insensitive comparisons of localparts.  However, as a practical matter,
I think this is one of those issues where you have to be "liberal in
what you accept, conversative in what you send."

I'm very careful to retain case settings (got that wrong once, too, many
years ago) and I do case insensitive comparisons of localparts, but only
after the domains match.  This doesn't make it right, but I'm also
careful to note duplicates so if there were two subscribers with the
"same" localpart but with different case settings, it would get noticed
immediately.  Thus, in this case, I have a fail-safe so I'm comfortable
doing it with automation.

You're right about the lack of filtering standards and I for one think
we should change that.

Jim

On Thu, 1 Feb 2001, Keith Moore wrote:

    Date: Thu, 01 Feb 2001 16:08:08 -0500
    From: Keith Moore <[email-masked]>
    To: James M Galvin <[email-masked]>
    Cc: Keith Moore <[email-masked]>, [email-masked], [email-masked],
         [email-masked]
    Subject: Re: Mail sent to midcom (fwd)

    

    

    
    Keith

---

From: Keith Moore <[email-masked]>
Date: Fri, 02 Feb 2001 11:11:41 -0500

Jim,

I agree that it's wrong to assuming that "." is a separator, but if 
you have a subscriber named "xxx.yyy@zzz", how likely is it really 
that a posting from "xxx@zzz" is spam?   

Keith

---

From: James M Galvin <[email-masked]>
Date: Fri, 02 Feb 2001 11:46:23 -0500 (EST)

Aah, I wasn't seeing your heuristic correctly before.  I agree, the
probability such a thing is spam is pretty low, and the downside of
getting it wrong is "harmless" enough.  So, you could even automate such
a thing.

The ding that I got in this "parsing localpart space" was unsubscribing
"xxx.yyy@zzz" because I assumed that "xxx@zzz" was a match.
Fortunately, I've always sent "good-bye" messages so the mistake was
caught more or less immediately, but it really turned me off to
localpart parsing, which, spam filtering aside, I still think is wrong.

Jim

---

From: Michael Richardson <[email-masked]>
Date: Fri, 02 Feb 2001 13:30:39 -0500

>> from people reporting problems.

    Keith> if the list is set up right, people don't have to report such problems.    
    Keith> the suspect messages go to the moderator; the moderator either approves

  The daily reports are about tcpdump, not about problems on the list.

    Keith> them or not based on whether they're on topic for the list.  if they
    Keith> are, the moderator can add the poster's address to the list of those
    Keith> who can post withut moderation.

  That is *exactly* what happens.

    Keith> adding support for recognizing subaddresses just optimizes this
    Keith> process - the moderator doesn't have to deal with quite so many

  Yes. Many mailers do this.

  Mailman at IETF won't even let me subscribe with a subaddress, since
it uses the SMTP From: to determine subscription.

---

From: Dave Crocker <[email-masked]>
Date: Fri, 02 Feb 2001 15:16:36 -0800

>remember a time when it wasn't true.

MUST be opaque, not should be.

Not only has it always been true, but it has usually caused problems when 
violated.

The language in RFC822bis 
<http://www.ietf.org/internet-drafts/draft-ietf-drums-msg-fmt-09.txt> is 
definitive, though not as obnoxiously forceful as seems to be needed, to 
make the point for this thread:

>>3.4.1. Addr-spec specification
>>...
>>
>>The local-part portion is a domain dependent string. In addresses, it is
>>simply interpreted on the particular host as a name of a particular
>>mailbox.

Firewalls and proxies are exceptions that I personally explain in terms of 
their being authorized on behalf of the "particular host".  There is some 
operational fantasy to that explanation, given that the agents are 
typically operated by a different group than the ones running the email 
user software, but it is the real theory that such agent services work on.

That it, such agents are part of a common administrative domain which 
authorizes their messing with the data.

Stray relays and services that are out it the great beyond of the general 
Internet are NOT so authorized.  They are MUCH more likely to interpret the 
local-part incorrectly

d/