Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 13 Feb 2001 14:58:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 13 Feb 2001 14:58:11 -0500 Received: from limes.hometree.net ([194.231.17.49]:14914 "EHLO limes.hometree.net") by vger.kernel.org with ESMTP id ; Tue, 13 Feb 2001 14:57:55 -0500 To: linux-kernel@vger.kernel.org Date: Tue, 13 Feb 2001 19:52:29 +0000 (UTC) From: "Henning P. Schmiedehausen" Message-ID: <96c39t$o1g$1@forge.intermeta.de> Organization: INTERMETA - Gesellschaft fuer Mehrwertdienste mbH In-Reply-To: <95ulrk$aik$1@forge.intermeta.de>, Reply-To: hps@tanstaafl.de Subject: Re: DNS goofups galore... Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org james@and.org (James Antill) writes: >"Henning P. Schmiedehausen" writes: >> % telnet mail.bar.org smtp >> 220 mail.foo.org ESMTP ready >> ^^^^^^^^^^^^ >> >> This kills loop detection. Yes, it is done this way =%-) and it breaks >> if done wrong. > This is humour, yeh ? No. > I would be supprised if even sendmail assumed braindamage like the >above. > For instance something that is pretty common is... >foo.example.com. IN A 4.4.4.4 >foo.example.com. IN MX 10 mail.example.com. >foo.example.com. IN MX 20 backup-mx1.example.com. >; This is really mail.example.org. >backup-mx1.example.com. IN A 1.2.3.4 No. This is a misconfiguration. Yes, RFC821 is a bit rusty but as far as I know, nothing has superseded it yet. And Section 3.7 states clearly: Whenever domain names are used in SMTP only the official names are used, the use of nicknames or aliases is not allowed. And the 220 Message is defined as 220 On sendmail, this is enforced by the "k" flag in the mailer definition. >...another is to have "farms" of mail servers (the A record for the MX >has multiple entries). > If it "broke" as you said, then a lot of mail wouldn't be being routed. You're correct. A lot of mail isn't routed or just routed because the mailers believe in the "be liberal in what you accept" policy. Or plainly non-RFC-compliant. There is a concept behind CNAMEs just like behind IP Fragmentation and the NT domains. Noone stated that it is a _SANE_ concept but it is now here and we have to live with it. CNAMES ARE NOT ALIASES. A CNAME is a reference. It states "the canonical name of "xxxx" is podunk.org". You write it as xxx IN CNAME podunk.org. SMTP requests that you use the canonical name in the 220 greeting, according to RFC 821. Everything else is misconfiguration. Regards Henning -- Dipl.-Inf. (Univ.) Henning P. Schmiedehausen -- Geschaeftsfuehrer INTERMETA - Gesellschaft fuer Mehrwertdienste mbH hps@intermeta.de Am Schwabachgrund 22 Fon.: 09131 / 50654-0 info@intermeta.de D-91054 Buckenhof Fax.: 09131 / 50654-20 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/