Great Circle Associates List-Managers
(December 2001)

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Subject: Re: List-ID
From: Norbert Bollow <nb @ thinkcoach . com>
Date: Mon, 3 Dec 2001 11:54:44 +0100
To: List-Managers @ GreatCircle . COM
In-reply-to: <87581031 . 1007291638 @ [192 . 168 . 0 . 4]> (message from Tom Neff on Sun, 02 Dec 2001 11:13:58 -0500)
Prefer-language: de, en, fr
References: <200112020900 . BAA05451 @ honor . greatcircle . com> <87581031 . 1007291638 @ [192 . 168 . 0 . 4]>

Tom Neff <tneff @
 panix .
 com> wrote:

> Is List-ID really useful in procmail rules?  First let's remember the 
> examples of valid List-ID's given in the RFC:
> 	List-Id: List Header Mailing List <>
> 	List-Id: <>
> 	List-Id: "Lena's Personal Joke List"
> 		<lenas-jokes.da39efc25c530ad145d41b86f7420c3b.021999.localhost>
> 	List-Id: "An internal CMU List" <>
> 	List-Id: <da39efc25c530ad145d41b86f7420c3b.052000.localhost>
> [Note to reader: Quick - without cheating - does YOUR procmail rule handle 
> all of these?]

If procmail can't handle all of these with a simple rule, then
that's a usability problem of procmail, which should be fixed
in one of the next versions of procmail.

> The RFC contradicts itself by saying "the owner of a mailing
> list MUST NOT generate list identifiers in any domain
> namespace for which they do not have authority," but later
> "...the mailing list administrator SHOULD avoid changing the
> list identifier even when the host serving the list changes."
> Which means that when you move your list from GreatCircle to
> HIS.COM, you're supposed to do what?

Contact GreatCircle and ask for permission to continue using the
old list identifier even though the list is no longer hosted at
GreatCircle.  When GreatCircle says "yes", this effectively
transfers to you authority over the { <> }

> Continue poaching on GreatCircle's namespace to which you're no 
> longer entitled, risking collision when some new legitimate GreatCircle 
> member wants to create sf-news which was your list's name?

They can create a new list named sf-news, but they MUST NOT
use as ListID unless GreatCircle first
contacts you to revoke your authority over the
{ <> } namespace.  If you want to prevent
the possibility of that happening in an unpleasant way, make a
contract with GreatCircle.

> That's assuming you even get to choose - many list hosters
> will probably have rigid ID generation schemes that will force
> a change when they decide (even if you aren't moving).

That problem will solve itself, over time.  If my competitors
can't be bothered to get the ListID: header right, that will
just make it easier for me to convince their customers to move
to my list-hosting service, until all surviving list-hosting
services understand that in order to be competitive, one had
better get the headers right.

> Third, there's content.  According the the RFC, this List-ID should apply 
> to all messages specific to the list.  That means, for example, that I 
> can't use List-ID to pull off postings for an archiver, because mixed in 
> will be adds and drops, rosters, membership reminders, moderation 
> notifiers, and all manner of other dripdrap.  To get anything useful done, 
> I'm going to have to apply heuristic context-type filters, exactly as I am 
> doing now.

ListID: doesn't single-handedly solve all problems, but it'll be
a useful thing to add into your heuristic algorithm in some way,
especially if you have multiple lists with similar subject matter.

> Fourth, say hello to the pass-through problem.  When one list feeds 
> another, the originating List-ID should survive, according to the RFC. 

Yes.  The subscriber is effectively subscribed to the feeding
list, although indirectly.

However if the feeding list is only an internal mechanism for
preparing some of the messages for the publicly-accessible list,
something that your subscribers don't want to know about, then
you should make sure that the List-ID: headers of the feeding
list don't leak out.

> When and if it becomes widespread, it will rocket to the top
> of the "troubleshooting" forums for users. managers and
> developers alike.

No.  It can't possibly make mail filtering more complicated or
error-prone than it is without the List-ID: header.

Greetings, Norbert.

A member of FreeDevelopers and the DotGNU Steering Committee:
Norbert Bollow, Weidlistr.18, CH-8624 Gruet   (near Zurich, Switzerland)
Tel +41 1 972 20 59       Fax +41 1 972 20 69
Your own domain with all your Mailman lists: $15/month

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