SQLGREY(1) User Contributed Perl Documentation SQLGREY(1)NAMEsqlgrey - Postfix Greylisting Policy Server
SYNOPSISsqlgrey [options...]
-h, --help display this help and exit
--man display man page
--version output version information and exit
-d, --daemonize run in the background
-p, --pidfile=FILE write process ID to FILE
(overrides 'pidfile' in configfile)
-k, --kill kill a running sqlgrey
(identified by 'pidfile' content)
-f, --configfile=FILE read config from FILE
(default /usr/local/etc/sqlgrey/sqlgrey.conf)
expecting config_param=value lines,
- spaces are ignored,
- '#' is used for comments
See the default config file at /usr/local/etc/sqlgrey/sqlgrey.conf for
runtime parameters. If you got sqlgrey from sources, read the HOWTO
file in the compressed archive. If it came prepackaged, look into the
documentation tree for this file: /usr/share/doc/sqlgrey-<version>/ on
most Linux distributions for example.
DESCRIPTION
Sqlgrey is a Postfix policy server implementing greylisting.
When a request for delivery of a mail is received by Postfix via SMTP,
the triplet "CLIENT_IP" / "SENDER" / "RECIPIENT" is built. If it is the
first time that this triplet is seen, or if the triplet was first seen
less than reconnect-delay minutes (1 is the default), then the mail
gets rejected with a temporary error. Hopefully spammers or viruses
will not try again later, as it is however required per RFC.
In order to alleviate the reconnect delay, sqlgrey uses a 2-level auto-
white-list (AWL) system:
· As soon as a "CLIENT IP" / "SENDER" is accepted, it is added to an
AWL. The couple expires when it isn't seen for more than awl-age
days (60 is the default).
· If group-domain-level "SENDER"s (2 is the default) from the same
domain or more use the same "CLIENT IP", another AWL is used based
on a "CLIENT IP" / "DOMAIN" couple. This couple expires after awl-
age days too. This AWL is meant to be used on high throughput sites
in order to :
· minimize the amount of data stored in database,
· minimize the amount of processing required to find an entry in
the AWL.
· don't impose any further mail delay when a "CLIENT IP" /
"DOMAIN" couple is known.
It can be disabled by setting group-domain-level to 0.
General idea:
When a SMTP client has been accepted once, if the IP isn't dynamic,
greylisting the IP again is only a waste of time when it sends another
e-mail. As we already know that this IP runs an RFC-compliant MTA (at
least the 4xx error code handling) and will get the new e-mail through
anyway.
In the case of mail relays, these AWLs works very well as the same
senders and mail domains are constantly coming through the same IP
addresses -> the e-mails are quickly accepted on the first try. In the
case of individual SMTP servers, this works well if the IP is fixed
too. When using a floating IP address, the AWLs are defeated, but it
should be the least common case by far.
Why do we put the domain in the AWL and not the IP only ? If we did
only store IP addresses, polluting the AWL would be far too easy. It
would only take one correctly configured MTA sending one e-mail from
one IP one single time to put it in a whitelist used whatever future
mails from this IP look like.
With this AWL system, one single mail can only allow whitelisting of
mails from a single sender from the same IP...
INSTALLATION
· Create a "sqlgrey" user. This will be the user the daemon runs as.
· When using a full-fledge SGBD (MySQL and PostgreSQL, not SQLite),
create a 'sqlgrey' db user and a 'sqlgrey' database. Grant access
to the newly created database to sqlgrey.
· Use the packaged init script to start sqlgrey at boot and start it
manually.
CONFIGURATION
General
· Start by adding check_policy_service after
reject_unauth_destination in /etc/postfix/main.cf :
smtpd_recipient_restrictions =
...
reject_unauth_destination
check_policy_service inet:127.0.0.1:2501
· Be aware that some servers do not behave correctly and do not
resend mails (as required by the standard) or use unique return
addresses. This is the reason why you should maintain whitelists
for them.
SQLgrey comes with a comprehensive whitelisting system. It can even
be configured to fetch up-to-date whitelists from a repository. See
the HOWTO for the details.
Disabling greylisting for some users
If you want to disable greylisting for some users you can configure
Postfix like this:
/etc/postfix/sqlgrey_recipient_access:
i_like_spam@ee.ethz.ch OK
Then you'll add a check_recipient_access in main.cf before the
check_policy_service :
smtpd_recipient_restrictions =
...
reject_unauth_destination
check_client_access hash:/etc/postfix/sqlgrey_client_access
check_recipient_access
hash:/etc/postfix/sqlgrey_recipient_access
check_policy_service inet:127.0.0.1:10023
SEE ALSO
See <http://www.greylisting.org/> for a description of what greylisting
is and <http://www.postfix.org/SMTPD_POLICY_README.html> for a
description of how Postfix policy servers work.
COPYRIGHT
Copyright (c) 2004 by Lionel Bouton.
LICENSE
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
AUTHOR
Lionel Bouton <lionel-dev@bouton.name>
perl v5.20.3 2016-02-18 SQLGREY(1)
