From owner-freebsd-doc@FreeBSD.ORG Mon Jan 21 04:42:18 2013 Return-Path: Delivered-To: freebsd-doc@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 1FE49BF for ; Mon, 21 Jan 2013 04:42:18 +0000 (UTC) (envelope-from lists@eitanadler.com) Received: from mail-lb0-f180.google.com (mail-lb0-f180.google.com [209.85.217.180]) by mx1.freebsd.org (Postfix) with ESMTP id 8965893F for ; Mon, 21 Jan 2013 04:42:16 +0000 (UTC) Received: by mail-lb0-f180.google.com with SMTP id gj3so4067234lbb.39 for ; Sun, 20 Jan 2013 20:42:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=eitanadler.com; s=0xdeadbeef; h=x-received:mime-version:in-reply-to:references:from:date:message-id :subject:to:cc:content-type; bh=LBtDAa07SyKwREgKuFgHeHzd++BTZjxdV+1BMAvQxMg=; b=hCrvpJ0lPE0V9NFHkia0WJqx35cR/MvHS4vo5kbfezmwdrns/iQYUbF81TnIfzFTcq Kp/LxOajyMWa0IElcDo4jmJdg0Ym0l+mUGl6aEXIJzfVhGz8iZ6ouw0sPDEj0mY7Zwkz hYAAuItLvbC9WwzVqYADXFm0W82BQ+WDUC/dM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=x-received:mime-version:in-reply-to:references:from:date:message-id :subject:to:cc:content-type:x-gm-message-state; bh=LBtDAa07SyKwREgKuFgHeHzd++BTZjxdV+1BMAvQxMg=; b=cinjB6RUgDpmg/9GLfP3jZqV7dR4+OGJN3m/ycrDZnqa9Wr0v5sh9pkQkMkInWQJn8 6iQ7UztaEwaWRrc/YkgIiZS7kFc7cNvQj0uoeSwO+4A8q5v5SoVvFM8xmR6OSP8pNFui qoHt6NBrSPKh+3hChCVzkG48/Hi+/Zt0wWmRzuoJf0M8IpXDbyInXGUjNAfPskvaEyfr RkcQa61sIvxfU1qGxY1CVo6jWq59eqVIR6DwNDVBUyT19A7RwTAGobgMO1NVjfyZDNTM 9TQx5l3VCUqb7IE01SzPzf207PVFIgJXFo8nD3C3lpUXkkM+jeHFZJoIoKomdvUejD25 q71Q== X-Received: by 10.112.46.37 with SMTP id s5mr6993925lbm.67.1358743335758; Sun, 20 Jan 2013 20:42:15 -0800 (PST) MIME-Version: 1.0 Received: by 10.112.100.164 with HTTP; Sun, 20 Jan 2013 20:41:45 -0800 (PST) In-Reply-To: References: From: Eitan Adler Date: Sun, 20 Jan 2013 23:41:45 -0500 Message-ID: Subject: Re: documenting the requirements for FreeBSD.org to send mail To: Warren Block Content-Type: text/plain; charset=UTF-8 X-Gm-Message-State: ALoCoQlFIHxI0jbpLIq0UjMN4Ip9zXozq62hPCF8aAjjN95e2XMEHyCGd/YIDIuopUUEuJ6z3UeL Cc: freebsd-doc@freebsd.org X-BeenThere: freebsd-doc@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Documentation project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 21 Jan 2013 04:42:18 -0000 On 17 January 2013 19:06, Warren Block wrote: > Typo (conneting). But that sentence is confusing. IP address to domain and > back to IP address which must match the original IP address? It was a poor attempt at condensing the following: === The problem I have with the above is that it appears to imply that DNS (only) establishes a one-to-one mapping between hostnames and IP addresses. This is not the case. In particular, it is not at all unusual for multiple hostnames to resolve to the same IP address; it is also not at all unusual for one hostname to resolve to a set of many IP addresses. Thus, it is possible to make use of these properties even if one lacks control over the in-addr.arpa zone for one's IP adddress, as long as there is a PTR record that points to a hostname, one of the IP addresses of which is the IP address currently being used for the SMTP conversation: mx1(8.3-P)[1] host mx.catwhisker.org mx.catwhisker.org has address 198.144.209.73 mx1(8.3-P)[2] host 198.144.209.73 73.209.144.198.in-addr.arpa domain name pointer m209-73.dsl.rawbw.com. mx1(8.3-P)[3] host m209-73.dsl.rawbw.com m209-73.dsl.rawbw.com has address 198.144.209.73 mx1(8.3-P)[4] As long as the above "looks consistent," (for a particular SMTP client), that meets the DNS requirements. And the above does meet the requirements. === -- Eitan Adler