1sqlgrey(1) User Contributed Perl Documentation sqlgrey(1)
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6 sqlgrey - Postfix Greylisting Policy Server
7
9 sqlgrey [options...]
10 -h, --help display this help and exit
12 --man display man page
13 --version output version information and exit
14 -d, --daemonize run in the background
15 -k, --kill kill a running sqlgrey
16 (identified by 'pidfile' content)
17 -f, --configfile=FILE read config from FILE
18 (default /etc/sqlgrey/sqlgrey.conf)
19 expecting config_param=value lines,
20 - spaces are ignored,
21 - '#' is used for comments
22 See the default config file at /etc/sqlgrey/sqlgrey.conf for runtime
24 parameters. If you got sqlgrey from sources, read the HOWTO file in
25 the compressed archive. If it came prepackaged, look into the documen‐
26 tation tree for this file: /usr/share/doc/sqlgrey-<version>/ on most
27 Linux distributions for example.
28
30 Sqlgrey is a Postfix policy server implementing greylisting.
31 When a request for delivery of a mail is received by Postfix via SMTP,
33 the triplet "CLIENT_IP" / "SENDER" / "RECIPIENT" is built. If it is the
34 first time that this triplet is seen, or if the triplet was first seen
35 less than reconnect-delay minutes (1 is the default), then the mail
36 gets rejected with a temporary error. Hopefully spammers or viruses
37 will not try again later, as it is however required per RFC.
38 In order to alleviate the reconnect delay, sqlgrey uses a 2-level auto-
40 white-list (AWL) system:
41 · As soon as a "CLIENT IP" / "SENDER" is accepted, it is added to an
43 AWL. The couple expires when it isn't seen for more than awl-age
44 days (60 is the default).
45 · If group-domain-level "SENDER"s (2 is the default) from the same
47 domain or more use the same "CLIENT IP", another AWL is used based
48 on a "CLIENT IP" / "DOMAIN" couple. This couple expires after awl-
49 age days too. This AWL is meant to be used on high throughput sites
50 in order to :
51 · minimize the amount of data stored in database,
53 · minimize the amount of processing required to find an entry in
55 the AWL.
56 · don't impose any further mail delay when a "CLIENT IP" /
58 "DOMAIN" couple is known.
59 It can be disabled by setting group-domain-level to 0.
61 General idea:
63 When a SMTP client has been accepted once, if the IP isn't dynamic,
65 greylisting the IP again is only a waste of time when it sends another
66 e-mail. As we already know that this IP runs an RFC-compliant MTA (at
67 least the 4xx error code handling) and will get the new e-mail through
68 anyway.
69 In the case of mail relays, these AWLs works very well as the same
71 senders and mail domains are constantly coming through the same IP
72 addresses -> the e-mails are quickly accepted on the first try. In the
73 case of individual SMTP servers, this works well if the IP is fixed
74 too. When using a floating IP address, the AWLs are defeated, but it
75 should be the least common case by far.
76 Why do we put the domain in the AWL and not the IP only ? If we did
78 only store IP addresses, polluting the AWL would be far too easy. It
79 would only take one correctly configured MTA sending one e-mail from
80 one IP one single time to put it in a whitelist used whatever future
81 mails from this IP look like.
82 With this AWL system, one single mail can only allow whitelisting of
84 mails from a single sender from the same IP...
85
87 · Create a "sqlgrey" user. This will be the user the daemon runs as.
88 · When using a full-fledge SGBD (MySQL and PostgreSQL, not SQLite),
90 create a 'sqlgrey' db user and a 'sqlgrey' database. Grant access
91 to the newly created database to sqlgrey.
92 · Use the packaged init script to start sqlgrey at boot and start it
94 manually.
95
97 General
98 · Start by adding check_policy_service after reject_unauth_destina‐
100 tion in /etc/postfix/main.cf :
101 smtpd_recipient_restrictions =
103 ...
104 reject_unauth_destination
105 check_policy_service inet:127.0.0.1:2501
106 · Be aware that some servers do not behave correctly and do not
108 resend mails (as required by the standard) or use unique return
109 addresses. This is the reason why you should maintain whitelists
110 for them.
111 SQLgrey comes with a comprehensive whitelisting system. It can even
113 be configured to fetch up-to-date whitelists from a repository. See
114 the HOWTO for the details.
115 Disabling greylisting for some users
117 If you want to disable greylisting for some users you can configure
119 Postfix like this:
120 /etc/postfix/sqlgrey_recipient_access:
122 i_like_spam@ee.ethz.ch OK
123 Then you'll add a check_recipient_access in main.cf before the
125 check_policy_service :
126 smtpd_recipient_restrictions =
127 ...
128 reject_unauth_destination
129 check_client_access hash:/etc/postfix/sqlgrey_client_access
130 check_recipient_access hash:/etc/postfix/sqlgrey_recipi‐
131 ent_access
132 check_policy_service inet:127.0.0.1:10023
133
135 See <http://www.greylisting.org/> for a description of what greylisting
136 is and <http://www.postfix.org/SMTPD_POLICY_README.html> for a descrip‐
137 tion of how Postfix policy servers work.
138
140 Copyright (c) 2004 by Lionel Bouton.
141
143 This program is free software; you can redistribute it and/or modify it
144 under the terms of the GNU General Public License as published by the
145 Free Software Foundation; either version 2 of the License, or (at your
146 option) any later version.
147 This program is distributed in the hope that it will be useful, but
149 WITHOUT ANY WARRANTY; without even the implied warranty of MER‐
150 CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
151 Public License for more details.
152 You should have received a copy of the GNU General Public License along
154 with this program; if not, write to the Free Software Foundation, Inc.,
155 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
156
158 Lionel Bouton <lionel-dev@bouton.name>
159perl v5.8.8 2007-03-13 sqlgrey(1)