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POSTGREY(1)	       User Contributed Perl Documentation	     POSTGREY(1)

NAME
     postgrey - Postfix Greylisting Policy Server

SYNOPSIS
     postgrey [options...]

      -h, --help	      display this help and exit
	  --version	      output version information and exit
      -v, --verbose	      increase verbosity level
	  --syslog-facility   Syslog facility to use (default mail)
      -q, --quiet	      decrease verbosity level
      -u, --unix=PATH	      listen on unix socket PATH
	  --socketmode=MODE   unix socket permission (default 0666)
      -i, --inet=[HOST:]PORT  listen on PORT, localhost if HOST is not specified
      -d, --daemonize	      run in the background
	  --pidfile=PATH      put daemon pid into this file
	  --user=USER	      run as USER (default: postgrey)
	  --group=GROUP       run as group GROUP (default: postgrey)
	  --dbdir=PATH	      put db files in PATH (default: /var/db/postgrey)
	  --delay=N	      greylist for N seconds (default: 300)
	  --max-age=N	      delete entries older than N days since the last time
			      that they have been seen (default: 35)
	  --retry-window=N    allow only N days for the first retrial (default: 2)
			      append 'h' if you want to specify it in hours
	  --greylist-action=A if greylisted, return A to Postfix (default: DEFER_IF_PERMIT)
	  --greylist-text=TXT response when a mail is greylisted
			      (default: Greylisted + help url, see below)
	  --lookup-by-subnet  strip the last N bits from IP addresses, determined by ipv4cidr and ipv6cidr (default)
	  --ipv4cidr=N	      What cidr to use for the subnet on IPv4 addresses when using lookup-by-subnet (default: 24)
	  --ipv6cidr=N	      What cidr to use for the subnet on IPv6 addresses when using lookup-by-subnet (default: 64)
	  --lookup-by-host    do not strip the last 8 bits from IP addresses
	  --privacy	      store data using one-way hash functions
	  --hostname=NAME     set the hostname (default: `hostname`)
	  --exim	      don't reuse a socket for more than one query (exim compatible)
	  --whitelist-clients=FILE     default: /usr/local/etc/postfix/postgrey_whitelist_clients
	  --whitelist-recipients=FILE  default: /usr/local/etc/postfix/postgrey_whitelist_recipients
	  --auto-whitelist-clients=N   whitelist host after first successful delivery
				       N is the minimal count of mails before a client is
				       whitelisted (turned on by default with value 5)
				       specify N=0 to disable.
	  --listen-queue-size=N        allow for N waiting connections to our socket
	  --x-greylist-header=TXT      header when a mail was delayed by greylisting
				       default: X-Greylist: delayed <seconds> seconds by postgrey-<version> at <server>; <date>

      Note that the --whitelist-x options can be specified multiple times,
      and that per default /usr/local/etc/postfix/postgrey_whitelist_clients.local is
      also read, so that you can put there local entries.

DESCRIPTION
     Postgrey 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
     delay seconds (300 is the default), then the mail gets rejected with a tem-
     porary error. Hopefully spammers or viruses will not try again later, as it
     is however required per RFC.

     Note that you shouldn't use the --lookup-by-host option unless you know
     what you are doing: there are a lot of mail servers that use a pool of ad-
     dresses to send emails, so that they can change IP every time they try
     again. That's why without this option postgrey will strip the last byte of
     the IP address when doing lookups in the database.

   Installation
     *	 Create a "postgrey" user and the directory where to put the database
	 dbdir (default: "/var/db/postgrey")

     *	 Write an init script to start postgrey at boot and start it. Like this
	 for example:

	  postgrey --inet=10023 -d

	 contrib/postgrey.init in the postgrey source distribution includes a
	 LSB-compliant init script by Adrian von Bidder for the Debian system.

     *	 Put something like this in /usr/local/etc/postfix/main.cf:

	  smtpd_recipient_restrictions =
			permit_mynetworks
			...
			reject_unauth_destination
			check_policy_service inet:127.0.0.1:10023

     *	 Install the provided postgrey_whitelist_clients and post-
	 grey_whitelist_recipients in /usr/local/etc/postfix.

     *	 Put in /usr/local/etc/postfix/postgrey_whitelist_recipients users that
	 do not want greylisting.

   Whitelists
     Whitelists allow you to specify client addresses or recipient address, for
     which no greylisting should be done. Per default postgrey will read the
     following files:

      /usr/local/etc/postfix/postgrey_whitelist_clients
      /usr/local/etc/postfix/postgrey_whitelist_clients.local
      /usr/local/etc/postfix/postgrey_whitelist_recipients

     You can specify alternative paths with the --whitelist-x options.

     Postgrey whitelists follow similar syntax rules as Postfix access tables.
     The following can be specified for recipient addresses:

     domain.addr
	       "domain.addr" domain and subdomains.

     name@     "name@.*" and extended addresses "name+blabla@.*".

     name@domain.addr
	       "name@domain.addr" and extended addresses.

     /regexp/  anything that matches "regexp" (the full address is matched).

     The following can be specified for client addresses:

     domain.addr
	       "domain.addr" domain and subdomains.

     IP1.IP2.IP3.IP4
	       IP address IP1.IP2.IP3.IP4. You can also leave off one number, in
	       which case only the first specified numbers will be checked.

     IP1.IP2.IP3.IP4/MASK
	       CIDR-syle network. Example: 192.168.1.0/24

     /regexp/  anything that matches "regexp" (the full address is matched).

   Auto-whitelisting clients
     With the option --auto-whitelist-clients a client IP address will be auto-
     matically whitelisted if the following conditions are met:

     *	 At least 5 successfull attempts of delivering a mail (after greylisting
	 was done). That number can be changed by specifying a number after the
	 --auto-whitelist-clients argument. Only one attempt per hour counts.

     *	 The client was last seen before --max-age days (35 per default).

   Greylist Action
     To set the action to be returned to postfix when a message fails postgrey's
     tests and should be deferred, use the --greylist-action=ACTION option.

     By default, postgrey returns DEFER_IF_PERMIT, which causes postfix to check
     the rest of the restrictions and defer the message only if it would other-
     wise be accepted.	A delay action of 451 causes postfix to always defer the
     message with an SMTP reply code of 451 (temp fail).

     See the postfix manual page access(5) for a discussion of the actions al-
     lowed.

   Greylist Text
     When a message is greylisted, an error message like this will be sent at
     the SMTP-level:

      Greylisted, see http://postgrey.schweikert.ch/help/example.com.html

     Usually no user should see that error message and the idea of that URL is
     to provide some help to system administrators seeing that message or users
     of broken mail clients which try to send mails directly and get a greylist-
     ing error. Note that the default help-URL contains the original recipient
     domain (example.com), so that domain-specific help can be presented to the
     user (on the default page it is said to contact postmaster@example.com)

     You can change the text (and URL) with the --greylist-text parameter. The
     following special variables will be replaced in the text:

     %s  How many seconds left until the greylisting is over (300).

     %r  Mail-domain of the recipient (example.com).

   Greylist Header
     When a message is greylisted, an additional header can be prepended to the
     header section of the mail:

      X-Greylist: delayed %t seconds by postgrey-%v at %h; %d

     You can change the text with the --x-greylist-header parameter. The follow-
     ing special variables will be replaced in the text:

     %t  How many seconds the mail has been delayed due to greylisting.

     %v  The version of postgrey.

     %d  The date.

     %h  The host.

   Privacy
     The --privacy option enable the use of a SHA1 hash function to store IPs
     and emails in the greylisting database.  This will defeat straight forward
     attempts to retrieve mail user behaviours.

   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) 2004-2007 by ETH Zurich. All rights reserved.  Copyright (c)
     2007 by Open Systems AG. All rights reserved.

LICENSE
     This program is free software; you can redistribute it and/or modify it un-
     der 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 FIT-
     NESS 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., 675
     Mass Ave, Cambridge, MA 02139, USA.

AUTHOR
     David Schweikert <david@schweikert.ch>

perl v5.42.3			   2026-08-30			     POSTGREY(1)

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