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- <title>HOWTO - Using the RBL</title>
+ <title>HOWTO - Using DNS Block Lists (DNSBLs)</title>
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- <h1>HOWTO - Using the RBL</h1>
+ <h1>HOWTO - Using DNS Block Lists (DNSBLs)</h1>
<p>The MAPS (Mail Abuse Protection System) RBL (Realtime Blackhole
- List) is a means of identifying hosts that have been associated
- with the sending of spam mail. A full description of the service
- and the technology and ethics behind it can be found at <a
- href="http://maps.vix.com/rbl/"><tt>http://maps.vix.com/rbl/</tt></a>
+ List) was the first application of a way of using a DNS list as a
+ means of identifying hosts that have been associated with the
+ sending of spam mail. A full description of the service and the
+ technology and ethics behind it can be found at <a
+ href="http://www.mail-abuse.org/rbl/"><tt>http://www.mail-abuse.org/rbl/</tt></a>
along with more general mail policy information at <a
- href="http://maps.vix.com/"><tt>http://maps.vix.com/</tt></a>.</p>
+ href="http://www.mail-abuse.org/"><tt>http://www.mail-abuse.org/</tt></a>.</p>
<p>In the few years since MAPS started operating, other similar
services although with different aims, procedures and
reliabilities have been introduced - MAPS itself has a number of
- these (ie MAPS/DUL which maintains lists of dial up modems), the
- other major source is <a href="http://www.orbs.org/">ORBS</a>,
- which is a more proactive relay blocking service</p>
+ these (ie MAPS/DUL which maintains lists of dial up modems). At
+ this point in time there are many 10s of services with varying
+ charters - lists of these can be found at <a
+ href="http://relays.osirusoft.com/"><tt>http://relays.osirusoft.com/</tt></a>
+ and <a
+ href="http://spamblock.outblaze.com/spamchk.html"><tt>http://spamblock.outblaze.com/spamchk.html</tt></a>.
+ The services are now normally referred to as a DNS Block List
+ (DNSBL), rather than RBLs, however you will find that earlier Exim
+ documentation (ie for version 3.x) will use the older term.</p>
- <p>Exim can use the MAPS RBL and/or any other similarly defined
- service (ie you could make your own additional maps as well). To
- use exim for this you need to be running version 1.80 or later,
- the configuration example in this document are specifically for
- version 3.00 and later - the old version of this document,
- covering older versions of exim can be found <a
- href="old_rbl.html">here</a>.</p>
-
- <h2>Exim RBL Support</h2>
+ <h2>Exim DNSBL Support</h2>
<p>Exim has supported RBL from version 1.80, although the
flexibility was increased (with a related change configuration
- options) on the release of Exim 3.00</p>
+ options) on the release of Exim 3.00. With the release of Exim
+ 4.00 the whole basis of policy checks on incoming mail changed
+ to be based on a set of Access Control Lists (ACLs) applied at
+ various during the incoming mail transaction. For this reason
+ the configuration of Exim 4.x and later to use DNSBLs is
+ complete different to that used for earlier versions.</p>
+
+ <h2>Exim 4.x DNSBL Usage</h2>
+
+ <p>In Exim 4.x a DNSBL lookup can be used in any of the incoming SMTP
+ ACLs. However it is typical for the lookups to be used in the ACL
+ handling <tt>RCPT TO</tt> - this allows policies to accept mail
+ for <tt>postmaster</tt> or other special local parts (for
+ example so a blocked sender can talk to the local postmaster
+ about getting blocks lifted or excluded)</p>
+
+ <p>The use of DNSBLs is substantially documented in the main exim
+ specification or the 4.x versions, so will not be covered in
+ detail here. However a couple of examples can be given</p>
+ <pre>
+ # Add a warning header if the sending host is in these
+ # DNSBLs but acccept the message (or rather leave it for
+ # later ACLs to accept/deny
+ warn message = X-blacklisted-at: $dnslist_domain
+ dnslists = blackholes.mail-abuse.org : \
+ dialup.mail-abuse.org
+
+
+
+ # Reject messages from senders listed in these DNSBLs
+ deny dnslists = blackholes.mail-abuse.org
+ </pre>
+
+ <p>Documentation on these features can be found in the
+ specification section on
+ <a href="../exim-html-4.20/doc/html/spec_37.html">
+ Access Control Lists</a>.</p>
+
+ <h2>Exim 3.x DNSBL Usage</h2>
<p>The exim RBL support allows one or more RBL systems to be
checked and messages from hosts within each RBL to be either
an RBL blocked site.</p>
- <h2>RBL Configuration Options</h2>
+ <h3>RBL Configuration Options</h3>
<p>These are fully detailed in the <a
- href="../exim-html-3.10/doc/html/spec.html" target="_top">Exim
+ href="../exim-html-3.20/doc/html/spec.html" target="_top">Exim
Specification Document</a>. The specific section on RBL is <a
- href="../exim-html-3.10/doc/html/spec_43.html#SEC758">here</a> and
+ href="../exim-html-3.20/doc/html/spec_46.html#SEC810">here</a> and
the rbl directives are documented starting <a
- href="../exim-html-3.10/doc/html/spec_11.html#SEC299">here</a></p>
+ href="../exim-html-3.20/doc/html/spec_11.html#SEC311">here</a></p>
<p>A typical configuration would be a mail system which rejects
- mail from machines that appear within the MAPS RBL list, and also
- checks hosts in the ORBS lists but only marking each message has
- coming via an RBLed host rather than rejecting them. Additionally
- all mail to the local postmaster always gets through, even if the
- host is in the MAPS RBL list. You also have a local private set
- of IPs which relay out through this mail server on net
- 192.168.0.0/24 - these cannot be contacted from outside your
- organisation so RBL is not an issue.</p>
+ mail from machines that appear within either the MAPS RBL list or
+ the MAPS DUL (Dial-Up List), and also checks hosts in the RSS
+ lists but only marking each message has coming via an RBLed host
+ rather than rejecting them. Additionally all mail to the local
+ postmaster always gets through, even if the host is in the MAPS
+ RBL list. You also have a local private set of IPs which relay
+ out through this mail server on net 192.168.0.0/24 - these cannot
+ be contacted from outside your organisation so RBL is not an
+ issue.</p>
<p>The configuration fragment (in the main part of the exim
configuration file) to do this is:-</p>
<pre>
-# reject messages whose sending host is in MAPS/RBL
-# add warning to messages whose sending host is in ORBS
-rbl_domains = rbl.maps.vix.com/reject : relays.orbs.org/warn
+# reject messages whose sending host is in MAPS/RBL & MAP/DUL
+# add warning to messages whose sending host is in RSS
+rbl_domains = blackholes.mail-abuse.org/reject : \
+ dialups.mail-abuse.org/reject : \
+ relays.mail-abuse.org/warn
# check all hosts other than those on internal network
rbl_hosts = !192.168.0.0/24:0.0.0.0/0
# but allow mail to postmaster@my.dom.ain even from rejected host
recipients_reject_except = postmaster@my.dom.ain
# change some logging actions (collect more data)
-rbl_log_headers # log headers of accepted RBLed messages
-rbl_log_rcpt_count # log recipient info of accepted RBLed messages
+rbl_log_headers # log headers of accepted RBLed messages
+rbl_log_rcpt_count # log recipient info of accepted RBLed messages
</pre>
<p>The information to do more complicated manipulations can be
<hr>
<address><a href="mailto:Postmaster@exim.org">Nigel Metheringham</a></address>
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