1milter-greylist(8)                                          milter-greylist(8)
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3
4

NAME

6       milter-greylist - grey listing filter for sendmail
7

SYNOPSIS

9       milter-greylist  [-A]  [-a autowhite_delay] [-c] [-D] [-d dumpfile] [-f
10       configfile] [-h] [-l] [-q] [-r]  [-S]  [-T]  [-u  username[:groupname]]
11       [-v]  [-w  greylist_delay] [-L cidrmask] [-M prefixlen] [-P pidfile] -p
12       socket
13

DESCRIPTION

15       milter-greylist is a mail filter  for  sendmail  that  implements  grey
16       listing, a spam filtering technique proposed by Evan Harris.
17
18       Grey  listing works by assuming that contrarily to legitimate MTA, spam
19       engines will not retry sending their junk mail on  a  temporary  error.
20       The  filter will always temporarily reject mail on a first attempt, and
21       accept it after some time has elapsed.
22
23       If spammers ever try to resend rejected messages, we  can  assume  they
24       will  not stay idle between the two sends. Odds are good that the spam‐
25       mer will send a mail to an honey pot address and get blacklisted  in  a
26       distributed black list before the second attempt.
27
28       Of  course,  the  filter can be configured to not apply grey listing to
29       some hosts or networks. You can whitelist friendly  SMTP  servers,  and
30       you should whitelist your own network, otherwise your SMTP clients will
31       have real trouble to send e-mail.  Whitelisting  localhost  is  also  a
32       must.
33
34       milter-greylist  works with two files.  greylist.conf is the configura‐
35       tion file. It holds the whitelist of addresses  that  will  not  suffer
36       grey  list  filtering.   It  is read once upon milter-greylist startup,
37       then it will be automatically reloaded whenever a new message  gets  in
38       and if it had been modified. You should not send milter-greylist a kill
39       -1 as it will just terminate it (libmilter works that way).
40
41       See greylist.conf(5) for documentation on the file's format.
42
43       The second file is greylist.db.  milter-greylist  will  regularly  dump
44       its  grey  list  database  into  this file, which is used on startup to
45       restore the previous grey list state. If the file does not exist or  is
46       unreadable, milter-greylist will start with an empty grey list.
47
48       The default location for the grey list database and the socket for com‐
49       municating with sendmail is /var/milter-greylist/.  That directory must
50       be owned and writeable by the user id under which milter-greylist runs.
51
52       The  following  options  are available; if present, they override their
53       equivalents specified in the configuration file:
54
55       -A     Normally, milter-greylist does not greylist  senders  that  suc‐
56              ceeded  SMTP  AUTH. This option disables that feature and causes
57              authentication to be ignored.  Equivalent to the  noauth  option
58              in the configuration file.
59
60       -a autowhite_delay
61              Configure auto-whitelisting. After a tuple (sender IP, sender e-
62              mail, recipient  e-mail)  has  been  accepted,  other  identical
63              tuples  will  get  accepted for autowhite_delay.  The default is
64              one day. Use zero to disable auto-whitelisting.  A suffix can be
65              added  to  specify seconds (s), minutes (m), hours (h), days (d)
66              or weeks (w). Without any suffix, values are treated as seconds.
67              Equivalent to the autowhite option in the configuration file.
68
69       -c     Only check the configuration file and exit. Return value is 0 if
70              the configuration is valid, or an error  code  from  <sysexit.h>
71              otherwise.
72
73       -D     Do  not  fork; run in the foreground instead. Without this flag,
74              milter-greylist will become a daemon.  Equivalent to  the  node‐
75              tach option in the configuration file.
76
77       -d dumpfile
78              Location   of   the   dump  file.  Default  is  /var/lib/milter-
79              greylist/db/greylist.db.  Equivalent to the dumpfile  option  in
80              the configuration file.
81
82       -f configfile
83              Location of the config file. Default is /etc/mail/greylist.conf.
84
85       -h     Show usage information.
86
87       -L cidrmask
88              Use  cidrmask  as  a  matching mask when checking IPv4 addresses
89              entries in the greylist. This is aimed as a workaround  to  mail
90              farms that re-emit messages from different IP addresses. With -L
91              24, the matching mask is 255.255.255.0, and all addresses within
92              the  same class C network are considered the same. Default is -L
93              32, which corresponds to all addresses considered different.
94
95       -M prefixlen
96              Use prefixlen as a matching mask when  checking  IPv6  addresses
97              entries  in  the greylist. This is aimed as a workaround to mail
98              farms that re-emit messages from different IP addresses. With -M
99              64,   the   matching  mask  is  ffff:ffff:ffff:ffff::,  and  all
100              addresses within  the  same  subnet  are  considered  the  same.
101              Default  is -M 128, which corresponds to all IPv6 addresses con‐
102              sidered different.
103
104       -l     Enable debug output in the access-list management code.
105
106       -P pidfile
107              write the daemon's PID to pidfile.  Equivalent  to  the  pidfile
108              option in the configuration file.
109
110       -p socket
111              Use socket as the socket used by sendmail(8) to communicate with
112              milter-greylist.
113
114       -q     Quiet mode.  milter-greylist will not tell SMTP clients how much
115              time  they  have  to  wait  before the message will be accepted.
116              Equivalent to the quiet option in the configuration file.
117
118       -r     Display milter-greylist  version  and  build  environment,  then
119              exit.
120
121       -S     If  milter-greylist was built with SPF support, then SPF-compli‐
122              ant senders bypass greylisting.  This flag causes messages to be
123              greylisted  regardless of whether they are SPF-compliant or not.
124              Equivalent to the nospf option in the configuration file.
125
126       -T     Enable test mode. This alters  the  meaning  of  rcpt  lines  in
127              greylist.conf,  so that only messages sent to recipient adresses
128              listed there are selected for greylisting. This option  and  the
129              rcpt  lines  have been deprecated in favor of ACL, so do not use
130              it.
131
132       -u username[:groupname]
133              Drop root privileges and  switch  to  username  (and  optionally
134              groupname)  credentials.  Make  sure  this  user (and group) has
135              write access to greylist.db.  Equivalent to the user  option  in
136              the configuration file.
137
138       -v     Enable  debug  output.   milter-greylist will send messages (and
139              debug output if it is given the  -v  flag)  to  syslogd(8)  with
140              facility LOG_MAIL.  Equivalent to the verbose option in the con‐
141              figuration file.
142
143       -w greylist_delay
144              sets the minimum delay between the first attempt  and  the  time
145              the  message  can  be accepted. Default is 30 minutes.  A suffix
146              can be added to specify seconds (s),  minutes  (m),  hours  (h),
147              days  (d)  or weeks (w). Whithout any suffix, values are treated
148              as seconds.  Equivalent to the greylist option in the configura‐
149              tion file.
150

GREYLIST MX SYNC

152       milter-greylist  is  now able to sync the greylist between multiple MX.
153       In order to enable this feature, you need  to  list  the  peer  MXs  in
154       greylist.conf(5) like this:
155
156         peer 192.0.2.17
157         peer 192.0.2.18
158
159       When  peers  are  configured,  milter-greylist  will listen on the port
160       defined for the mxglsync service in /etc/services (defaults  to  5252),
161       and  it will connect to peers at this port. Each time an entry is added
162       or deleted on one MX, it will be propagated to the others.
163
164       The protocol is quite simple, just telnet to your MX at port 5252,  and
165       type  help  to  see  how  it  works. Note that connections will only be
166       accepted from peer MXs, even localhost will be rejected (and don't ever
167       add  localhost  as  a peer for MX sync, as you will cause each entry in
168       the greylist to be added twice).
169
170       If an MX is down, changes to the greylist will be queued until it  gets
171       back  up  again. The queue length is limited (default is 1024 entries),
172       and if it overflows, newer entries will be discarded.
173

AUTHORS

175       Emmanuel Dreyfus <manu@netbsd.org>
176
177       milter-greylist  received  many  contributions  from  (in  alphabetical
178       order):  Aida  Shinra,  Adam  Katz,  Alexander  Lobodzinski,  Alexandre
179       Cherif, Alexey Popov, Andrew McGill, Attila Bruncsak, Benoit Branciard,
180       Bernhard  Schneider,  Bob  Smith,  Constantine  A.  Murenin,  Christian
181       Pelissier, Cyril Guibourg, Dan Hollis, Elrond,  Enrico  Scholz,  Eugene
182       Crosser,  Fabien  Tassin, Fredrik Pettai, Gary Aitken, Georg Horn, Gert
183       Doering, Greg Troxel, Guido Kerkewitz, Hajimu Umemoto, Hideki ONO, Ivan
184       F. Martinez, Jacques Beigbeder, Jean Benoit, Jeff Rife, Jobst Schmalen‐
185       bach, Joe Pruett, Joel Bertrand, Johann E. Klasek, Johann Klasek,  John
186       Thiltges,  Klas  Heggemann,  Laurence Moindrot, Lev Walkin, Manuel Bad‐
187       zong, Martin Paul,  Matt  Kettler,  Mattheu  Herrb,  Matthias  Scheler,
188       Matthieu  Herrb,  Michael  Fromme, Moritz Both, Nerijus Baliunas, Pavel
189       Cahyna, Per Holm, Petr Kristof, Ralf S. Engelschall, Ranko  Zivojnovic,
190       Remy  Card,  Rick  Adams,  Rogier  Maas,  Romain Kang, Rudy Eschauzier,
191       Stephane Lentz, Thomas Scheunemann, Tim Mooney, Wolfgang Solfrank,  and
192       Yaroslav Boychuk.
193
194       Thanks  to  Helmut  Messerer  and Thomas Pfau for their feedback on the
195       first releases of this software.
196

SEE ALSO

198       greylist.conf(5), sendmail(8), syslogd(8).
199
200       Evan Harris's paper:
201              http://projects.puremagic.com/greylisting/
202
203       milter-greylist's web site:
204              http://hcpnet.free.fr/milter-greylist/
205
206
207
208                                 May 10, 2005               milter-greylist(8)
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