Date: Thu, 5 Jan 2017 09:58:21 +0100 From: Matthias Fechner <idefix@fechner.net> To: freebsd-questions@freebsd.org Subject: Re: Filtering Email Message-ID: <99370884-b547-c3c7-7b2b-711cedcedf27@fechner.net> In-Reply-To: <9bd488a3-ca45-a546-3706-3b032386f954@FreeBSD.org> References: <2E557AFF-35A1-4D08-8FA9-10C65BF4ABDE@lafn.org> <9bd488a3-ca45-a546-3706-3b032386f954@FreeBSD.org>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --5iScaiH1mjA70tx1HGVDqjSB5jGxI9ipH Content-Type: multipart/mixed; boundary="k5B2OiaU3IHx3hgVcNXU8cUtRuobeIl9X"; protected-headers="v1" From: Matthias Fechner <idefix@fechner.net> To: freebsd-questions@freebsd.org Message-ID: <99370884-b547-c3c7-7b2b-711cedcedf27@fechner.net> Subject: Re: Filtering Email References: <2E557AFF-35A1-4D08-8FA9-10C65BF4ABDE@lafn.org> <9bd488a3-ca45-a546-3706-3b032386f954@FreeBSD.org> In-Reply-To: <9bd488a3-ca45-a546-3706-3b032386f954@FreeBSD.org> --k5B2OiaU3IHx3hgVcNXU8cUtRuobeIl9X Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Am 05.01.2017 um 09:12 schrieb Matthew Seaman: > There's a potential problem with rejecting email from your local server= > -- backscatter. If your upstream MTA has accepted a message for > delivery and then your local MTA later decides to bounce it, there is n= o > choice other than to send the bounce to the sender address in the mail > headers, and spammers nowadays forge that address, so you end up > resending the spam to some (possibly innocent) third party. It's bette= r > to just /dev/null the messages in such circumstances. hm, this is really dangerous, you could kill by this action real email without notify the sender. I would recommend that the sender set a SPF record to control which server is allowed to use their domain. This would mitigate this problem and forge of email headers is not possible anymore. Gru=C3=9F Matthias --=20 "Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the universe trying to produce bigger and better idiots. So far, the universe is winning." -- Rich Cook --k5B2OiaU3IHx3hgVcNXU8cUtRuobeIl9X-- --5iScaiH1mjA70tx1HGVDqjSB5jGxI9ipH Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iEYEARECAAYFAlhuCroACgkQkZS/qRt1bvba8wCfb4mBrxlOAxuCYxnn6xw4HCww f+0AmwXwGkkEqhy0FXBXXtspXszgyXgq =G3Fp -----END PGP SIGNATURE----- --5iScaiH1mjA70tx1HGVDqjSB5jGxI9ipH--
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