From owner-freebsd-questions@FreeBSD.ORG Fri Apr 2 06:12:24 2010 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 5DC9F106566B for ; Fri, 2 Apr 2010 06:12:24 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from smtp.infracaninophile.co.uk (gate6.infracaninophile.co.uk [IPv6:2001:8b0:151:1::1]) by mx1.freebsd.org (Postfix) with ESMTP id DC05B8FC15 for ; Fri, 2 Apr 2010 06:12:23 +0000 (UTC) Received: from seedling.black-earth.co.uk (seedling.black-earth.co.uk [81.187.76.163]) (authenticated bits=0) by smtp.infracaninophile.co.uk (8.14.4/8.14.4) with ESMTP id o326CIKI066797 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO) for ; Fri, 2 Apr 2010 07:12:18 +0100 (BST) (envelope-from m.seaman@infracaninophile.co.uk) Message-ID: <4BB58AC2.50009@infracaninophile.co.uk> Date: Fri, 02 Apr 2010 07:12:18 +0100 From: Matthew Seaman Organization: Infracaninophile User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.1.9) Gecko/20100317 Thunderbird/3.0.4 MIME-Version: 1.0 To: freebsd-questions@freebsd.org References: <201004011751.27767.npapke@acm.org> In-Reply-To: <201004011751.27767.npapke@acm.org> X-Enigmail-Version: 1.0.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Virus-Scanned: clamav-milter 0.95.3 at happy-idiot-talk.infracaninophile.co.uk X-Virus-Status: Clean X-Spam-Status: No, score=-1.1 required=5.0 tests=BAYES_00,DKIM_ADSP_ALL, SPF_FAIL autolearn=no version=3.3.0 X-Spam-Checker-Version: SpamAssassin 3.3.0 (2010-01-18) on happy-idiot-talk.infracaninophile.co.uk Subject: Re: Sendmail Five Second Greeting Delay X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 02 Apr 2010 06:12:24 -0000 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 02/04/2010 01:51:27, Norbert Papke wrote: > When I connect to sendmail on a local interface, sendmail responds to the > connection with its "220" greeting immediately. If I connect to sendmail from > another machine on my (home) LAN, sendmail delays five seconds before sending > the greeting. I would like it to respond immediately. > A quick search turned up a "greet_delay" feature in sendmail that would cause > this type of behavior. To the best of my knowledge, I do not use this > feature. Just to be sure, I tried to explicitly enable it with both a default > 0 second timeout and an explicit 0 second access rule. This did not the > resolve the issue. For the sake of the archives, I'd like to note that the `greet_pause' feature is actually a pretty effective and very cheap to implement anti-spam measure. You need: FEATURE(greet_pause, `5000')dnl ## 5 seconds in your $(hostname).mc file -- this gives you a default 5 second delay. If you also have FEATURE(`access_db') you can override that value for particular IP ranges or domain names. This is also a handy addition to the .mc file: LOCAL_RULESETS SLocal_greet_pause R$* $: $&{daemon_flags} R$* a $* $# 0 This turns off greet_pause on network ports where authentication is required, ie. if you use port 587 for submitting new mail and reserve port 25 for MTA to MTA mail transfers. The way this works is that it requires the sending side to wait until your system prints out the greeting banner. If the sending side starts speaking before then, sendmail will refuse to accept any mail during that session. All real MTAs will get this right, as it is part of the SMTP specification in the RFCs. Many spambots on the other hand, send e-mail by simply replaying one side of a recorded SMTP conversation without reguard for what the other side says. This feature weeds out that sort of spambot with very little effort. Cheers, Matthew - -- Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard Flat 3 PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate Kent, CT11 9PW -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.14 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAku1isIACgkQ8Mjk52CukIxZHgCfYCSyseFoQ+M89C1kJIt+Oq8n bKcAoIpNrzUS2xN3ZGGZ889qLZq6TRmD =U4Ip -----END PGP SIGNATURE-----