update spam countermeasures
add examples of using an access_db
update .mc files to match recommendations on
http://www.sendmail.org/m4/anti-spam.html
(grrr.....should have been one commit
did the last commit from a subdirectory)
This commit is contained in:
Jonathan M. Bresler
parent
54919b86a0
commit
762003080e
@ -1,13 +1,6 @@
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# $Id: Makefile,v 1.5 1998/09/13 23:14:20 brian Exp $
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# $Id: Makefile,v 1.6 1999/01/31 15:21:15 jmb Exp $
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install:
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/usr/sbin/makemap hash /etc/mail/spamsites < /etc/mail/block_domains.txt
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.if exists(/etc/mail/spamsites.local)
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/usr/sbin/makemap -o hash /etc/mail/spamsites < /etc/mail/spamsites.local
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.endif
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/usr/sbin/makemap hash /etc/mail/denyip < /etc/mail/block_ips.txt
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.if exists(/etc/mail/denyip.local)
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/usr/sbin/makemap -o hash /etc/mail/denyip < /etc/mail/denyip.local
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.endif
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/usr/sbin/makemap hash /etc/mail/access < /etc/mail/access.txt
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all: install
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@ -1,74 +1,17 @@
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# $Id: README,v 1.5 1998/09/02 01:34:57 brian Exp $
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# $Id: README,v 1.5.2.1 1999/05/01 03:37:29 jkh Exp $
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Filtering out SPAM from your site
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Sendmail now includes excellent tools block spam. These
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tools are available as FEATUREs that you can add to your site's
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.mc file. Proper use of these FEATUREs will prevent spammer from
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using your site as a relay as well as significantly decrease the
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amount of spam that arrives at your site. No set of anti-spam
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tools will block all spam without blocking some portion of legitimate
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mail as well. Therefore, these FEATUREs are designed to prevent
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as much spam as possible without blocking legitimate mail.
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Introduction:
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The FreeBSD Project filters spam, unsolicited commerical
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e-mail, from its mailing lists. The filter has two parts: databases
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and rulesets. We have rulesets to /etc/sendmail.cf, check_rcpt,
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check_relay, check_rbl, check_mail and xlat. (xlat is for testing
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only, as explained in /etc/mail/sendmail.cf.additions.) These
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rulesets use three databases. The denyip, a list of IP addresses,
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spamsites, a list of domains, and fakenames, a list of bogus
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usernames (such as investor and success). We do not accept mail
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from any machine that matches a entry in either database, or users
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in the fakenames database.
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These tools are discussed in /usr/src/contrib/sendmail/cf/README.
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Read the section entitled "ANTI-SPAM CONFIGURATION CONTROL". Example
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usage and additional tools can be found in
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/usr/src/contrib/sendmail/cf/cf/knecht.mc.
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Filtering at your site:
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To filter spam at your site you need to:
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1. modify your /etc/sendmail.cf,
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2. create a list of domains/ips you wish to block
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3. make the databases and
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4. finally signal sendmail that the configuration file has changed.
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1. Modifying your /etc/sendmail.cf
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Add the database declarations and the rulesets contained
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in /etc/mail/sendmail.cf.additions to your .mc file. If you do
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not use m4 to generate your /etc/sendmail.cf, add the database
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declarations to your /etc/sendmail.cf.
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2. Put the list of domains you wish to block in /etc/mail/spamsites
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3. Make the databases:
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As root, type "cd /etc/mail; make install" will build the
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two databases from the retrieved source files and the local additions
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files.
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4. Signaling sendmail:
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Sendmail will reread its configuration whenever sendmail
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receives a HUP signal. As root, type "kill -HUP `cat
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/var/run/sendmail.pid`". Check sendmail's log file to be sure that
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it has restarted. /var/log/maillog should contain the line: "Oct
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15 08:59:16 hub sendmail[6565]: restarting /usr/sbin/sendmail on
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signal". Most likely, the date, time, hostname and process id will
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be differ.
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Testing the spam filter:
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How can I tell if its working:
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The mail log file, /var/log/maillog, will contain a line
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for every message filtered. The lines will be similar to one of
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these two log entries:
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Check_mail rejects:
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Oct 15 02:43:26 hub sendmail[6565]: CAA06565: ruleset=check_mail,
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arg1=<announce@martianconsulate.com>, relay=xxx.isp.net [###.###.###.###],
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reject=521 <announce@martianconsulate.com>
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Nov 30 15:56:37 hub sendmail[15058]: PAA15058: ruleset=check_mail,
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arg1=<ultramax@s2.eddelwissl.NET>, relay=relay.somewhere.com
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[###.###.###.###], reject=451 <ultramax@s2.eddelwissl.NET>... Domain
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does not resolve
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Check_relay rejects:
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Oct 19 04:45:24 hub sendmail[3503]: NOQUEUE: ruleset=check_relay,
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arg1=imsp015.netvigator.com, arg2=205.252.144.206, relay=root@localhost,
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reject=521 blocked.contact postmaster@FreeBSD.ORG
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check_rcpt reject:
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Nov 30 15:04:08 hub sendmail[12390]: PAA12390: ruleset=check_rcpt,
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arg1=investor@100percent.per.year.com, relay=newfed.frb.gov
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[198.3.221.5], reject=553 investor@100percent.per.year.com...
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521<investor@100percent.per.year.com>#blocked.contact postmaster
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Sun Nov 16 11:40:53 PST 1997
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@ -1,125 +0,0 @@
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# $Id:$
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#
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# list of hosts and domains for whom we relay mail.
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# all .forward hosts, domains must be listed in this file.
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# same for hosts and domains in /etc/aliases
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F{LocalIP}-o /etc/mail/Local-IP
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F{RelayTo}-o /etc/mail/Relay-Hosts
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# database declarations
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Kdenyip hash -o -a.REJECT /etc/mail/denyip.db
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Kfakenames hash -o -a.REJECT /etc/mail/fakenames.db
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Kspamsites hash -o -a.REJECT /etc/mail/spamsites.db
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# helper rulsesets; useful for debugging sendmail configurations
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#
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#
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Scheck_rbl
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# lookup up an ip address in the Realtime Blackhole List.
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R$-.$-.$-.$- $: $(host $4.$3.$2.$1.rbl.maps.vix.com $:OK $)
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Sxlat # for sendmail -bt
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# sendmail treats "$" and "|" as two distinct tokens
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# this rule "pastes" them together into one token
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# and then calls check_relay.
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R$* $$| $* $: $1 $| $2
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R$* $| $* $@ $>check_relay $1 $| $2
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Scheck_relay
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# called with "hostname.tld $| IP address" of connecting host.
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# hostname.tld is the fully-qualified domain name
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# IP address is dotted-quad with surrounding "[]" brackets.
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#
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# each group of rules in this ruleset is independent.
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# each accepts and return "hostname.tld $| IP address"
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# use the ones that you want comment out the rest
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# you may rearrange the groups but not the rules in each group.
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# each group is preceded and followed by a comment
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#
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# host must NOT be in the "spamsites" database--BEGIN
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R$* $| $* $: <$1 $| $2> $1
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R<$*> $+.$+.$+ <$1> $3.$4
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R<$*> $+.$+ $: <$1> $(spamsites $2.$3 $)
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R<$*> $*.REJECT $#error $: 521 blocked. contact postmaster@$m
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R<$*> $* $: $1
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# host must NOT be in the "spamsites" database--END
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# ip address must NOT be in the "denyip" database--BEGIN
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R$* $| $* $: $1 $| $(denyip $2 $)
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R$* $| $*.REJECT $#error $: 521 blocked. contact postmaster@$m
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# ip address must NOT be in the "denyip" database--END
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R$* $@ OK
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Scheck_mail
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# called with envelope sender (everything after ":") in
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# "Mail From: xxx", of SMTP conversation
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# may or may not have "<" ">"
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# the groups of rules in this ruleset ARE NOT independent.
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# "remove all RFC-822 comments" must come first
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# "Connecting Host" and "Paul Vixie's RBL" must be last
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#
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# use the ones that you want comment out the rest
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# each group is preceded and followed by a comment
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#
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# remove all RFC-822 comments--BEGIN
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# MUST be first rule in check_mail rulseset.
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R$* $: $>3 $1
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# remove all RFC-822 comments--END
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# mail must come from a DNS resolvable host--BEGIN
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R$* < @ $+ . > $: $1 @ $2
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R$* < @ $+ > $#error $@ 4.1.8 $: "451 Domain does not resolve"
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# mail must come from a DNS resolvable host--END
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# mail must NOT come from a known source of spam--BEGIN
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R$+ @$+ $: <$1@$2> $2
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R<$*> $+.$+.$+ <$1> $3.$4
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R<$*> $* $: $(spamsites $2 $: OK $)
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R$+.REJECT $#error $@ 5.7.1 $: 550 $1
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R<$*> $* $: $1
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# mail must NOT come from a known source of spam--END
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# Connecting Host must resolve--BEGIN
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R$* $: $1 $: $(dequote "" $&{client_name} $)
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R$* $: $>3 foo@$1
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R<$*> $*<@$*> $#error $@ 4.1.8 $: "451 Domain does not resolve"
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# Connecting Host must resolve--END
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# ip address must NOT be in Paul Vixie's RBL--BEGIN
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R$* $: $1 $: $(dequote "" $&{client_addr} $)
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R$* $: $>check_rbl $1
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R$*.com. $#error $@ 5.7.1 $: "550 Mail refused, see http://maps.vix.com/rbl"
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# ip address must NOT be in Paul Vixie's RBL--END
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R$* $@ OK
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Scheck_rcpt
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# called with envelope recipient (everything after ":") in
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# "Rcpt To: xxx", of SMTP conversation
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# may or may not have "<" ">" and or RFC-822 comments.
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# let ruleset 3 clean this up for us.
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#
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# do NOT reorder these two groups of rules.
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# restrict mail relaying to host and domains listed in /etc/sendmail.cR
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#
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# mail must NOT be addressed "fakenames"--BEGIN
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R$* $: <$1> $>3 $1
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R<$*> $+ < @ $+ > $: <$1> $(fakenames $2 $: OK $)
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R$+.REJECT $#error $@ 5.2.1 $: 550 $1
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R<$*> $* $: $1
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# mail must NOT be addressed "fakenames"--END
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# mail must come from or go to this machine or machines we allow to relay--BEGIN
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# from http://www.informatik.uni-kiel.de/%7Eca/email/check.html#check_rcpt
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R$+ $: $(dequote "" $&{client_addr} $) $| $1
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R0 $| $* $@ ok
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R$={LocalIP}$* $| $* $@ ok
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# not local, check rcpt
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R$* $| $* $: $>3 $2
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# remove local part, maybe repeatedly
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R$+ $:$>removelocal $1
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# still something left?
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R$*<@$+>$* $#error $@ 5.7.1 $: 550 we do not relay
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#
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Sremovelocal
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# remove RelayTo part (maybe repeatedly)
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# R$*<@$*$={RelayTo}.>$* $>3 $1 $4
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R$*<@$=w.>$* $: $>removelocal $>3 $1 $3
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R$*<@$*>$* $@ $1<@$2>$3
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# dequote local part
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R$- $: $>3 $(dequote $1 $)
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R$*<@$*>$* $: $>removelocal $1<@$2>$3
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# mail must come from or go to this machine or machines we allow to relay--END
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