From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS6315 166.70.0.0/16 X-Spam-Status: No, score=-3.6 required=3.0 tests=AWL,BAYES_00, RCVD_IN_DNSWL_LOW,SPF_HELO_NONE,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from out03.mta.xmission.com (out03.mta.xmission.com [166.70.13.233]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id E8F391F4C0; Fri, 25 Oct 2019 03:31:13 +0000 (UTC) Received: from in02.mta.xmission.com ([166.70.13.52]) by out03.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1iNqJk-00010U-M6; Thu, 24 Oct 2019 21:31:12 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1iNqJj-0007HD-Su; Thu, 24 Oct 2019 21:31:12 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Eric Wong Cc: meta@public-inbox.org References: <20191025022800.GA29369@dcvr> Date: Thu, 24 Oct 2019 22:30:08 -0500 In-Reply-To: <20191025022800.GA29369@dcvr> (Eric Wong's message of "Fri, 25 Oct 2019 02:28:00 +0000") Message-ID: <87pniltscf.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1iNqJj-0007HD-Su;;;mid=<87pniltscf.fsf@x220.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/++MDoHraDK4z8wZYPvnA/1FttHw9Mkpk= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: what should happen when mda sees multiple List-ID headers? X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) List-Id: Eric Wong writes: > Given my recent traumatic experience[*] around multiple > From/To/Cc/Subject headers; I guess we should prepare for the > possibility of multiple List-ID headers showing up in -mda. > > Right now, we handle the first one (and I'm updating -learn to > support List-ID, too); but it's possible that multiple List-ID > header can map to different inboxes, too... So I looked at RFC2919 and it had something interesting to say. - That when you receive a message from a mailing list only the List-ID set by the mailling list software should be present. I think in practice that means if everything is RFC conformant and working correctly you should never see a message with multiple List-IDs. Which leads us to what should we do with potentially buggy software. Or possibly a creative list processor that realizes that handles multiple lists, sees that a message is cross-posted and sends out a single copy of it to the addresses that are subscribed to both lists. There are two reasonable things that can be done, and I suggest we do them both. - Print a warning. (To be deleted if this case turns out to be common). - Deliver to all of the lists you have mailboxes for the List-IDs. I think that would be the most robust response long term, and it is roughly what my code in import_imap_mailbox so I don't see it causing any problems at present. In particular the delivery logic I have been running with for a long time now is: my @dests = email_dest($config, $mime); for my $ibx (@dests) { my $im = PublicInbox::InboxWritable->new($ibx); die "no im" unless defined($im); $im->add($mime); } So I can say at worst it is harmless to have code that handles multiple List-ID headers. Eric