Postfix how to balance outgoing emails via multiple IP addresses

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Postfix how to balance outgoing emails via multiple IP addresses Postfix how to balance outgoing emails via multiple IP addressesThe solution is depending on postfix`s TCP_TABLES and a perl script. In my example I`m using 7 different IP address to route outgoingmails, make sure you`ve already the IP addresses you are going to use have been configured on your box.First get a recent postfix rpm from here http://ftp.wl0.org/official/2.9/RPMS-rhel5-x86_64/. This one is built for rhel5/centos5 however should be workingwithout much hassle on rhel6/centos5. Install the package:# rpm -Uvh postfix-2.9.1-1.rhel5.x86_64.rpmMake sure its built with tcp tables support:# postconf -mbtreecidrenvironfailhashinternalldapmemcachenisproxyregexpstatictcptexthashunixInstall the perl moduleList::util::WeightedRoundRobin:cpan install /List::util::WeightedRoundRobin/Create the following perl script and make it executable:vi /etc/postfix/random.pl#!/usr/bin/perl -w# author: Hari Hendaryanto use strict;use warnings;use Sys::Syslog qw(:DEFAULT setlogsock);useList::Util::WeightedRoundRobin;use Storable;my $hashfile=&quot;/tmp/file.hash&quot;;store {}, $hashfile unless -r $hashfile;## our transports lists, we will define this in master.cf as transport services# Queued using Weighted Round-Robin Scheduling#my $list = [{name=> 'smtp1:',weight => 1,},{name => 'smtp2:',weight => 1,},{name => 'smtp3:',weight => 1,},{name => 'smtp4:',weight => 1,},{name => 'smtp5:',weight => 1,},{name => 'smtp6:',weight => 1,},{name => 'smtp7:',weight => 1,},];my $WeightedList = List::Util::WeightedRoundRobin->new();my$weighted_list = $WeightedList->create_weighted_list( $list );# $maxinqueue max number of queue in smtp listmy $maxinqueue = scalar(@{$weighted_list});## Initalize and open syslog.#openlog('postfix/randomizer','pid','mail');## Autoflush standard output.#selectSTDOUT; $|&#43;&#43;;while (<>) {chomp;my $count;my $hash=retrieve($hashfile);if (!defined $hash->{&quot;index&quot;}){$count = 0;} else {$count = $hash->{&quot;index&quot;};}if ($count >= $maxinqueue){$hash->{&quot;index&quot;} = 0;$count = 0;}$hash->{&quot;index&quot;}&#43;&#43;;store $hash, $hashfile;my $random_smtp= ${$weighted_list}[$count];if (/^get\s(.&#43;)$/i) {print &quot;200 $random_smtp\n&quot;;syslog(&quot;info&quot;,&quot;Using: %s Transport Service&quot;, $random_smtp);next;}print &quot;200 smtp:\n&quot;;}Execute the script to make sure it`s working and no errors are encountered:/etc/postfix/random.plConfigurepostfix to use the random generated smtp transport.Edit /etc/postfix/master.cf, by appending following lines:## Round-robin outgoing smtp127.0.0.1:23000 inet n n n - 0 spawnuser=nobody argv=/etc/postfix/random.pl# random smtpsmtp1 unix - - n - - smtp-o syslog_name=postfix-smtp1-o smtp_helo_name=FQDN -o smtp_bind_address=IPsmtp2 unix - - n - - smtp-o syslog_name=postfix-smtp2-o smtp_helo_name= FQDN -o smtp_bind_address=IPsmtp3 unix - - n - - smtp-o syslog_name=postfix-smtp3 -o smtp_helo_name=FQDN -o smtp_bind_address=IPsmtp4 unix- - n - - smtp-o syslog_name=postfix-smtp4 -o smtp_helo_name=FQDN -o smtp_bind_address=IPsmtp5 unix - - n - - smtp-o syslog_name=postfix-smtp5 -o smtp_helo_name=FQDN -o smtp_bind_address=IPsmtp6 unix - - n - - smtp-o syslog_name=postfix-smtp6-o smtp_helo_name=FQDN -o smtp_bind_address=IPsmtp7 unix - - n - - smtp-o syslog_name=postfix-smtp7-o smtp_helo_name= FQDN -o smtp_bind_address=IPReplace FQDN with desired hostname and IP with the list of the IP addresses you`d like to use.Append the following lines to your/etc/postfix/main.cf:transport_maps = tcp:127.0.0.1:23000127.0.0.1:23000_time_limit = 3600sRestart/reload postfix and verify everything is working correctly:# postmap -q &quot;dummy&quot; tcp:127.0.0.1:23000smtp4:# postmap -q &quot;dummy&quot; tcp:127.0.0.1:23000smtp5:# postmap-q &quot;dummy&quot; tcp:127.0.0.1:23000smtp6:In your logs you should see the different smtp transport beeing used when mails are sent:Sep 2 12:50:05 myserver postfix-smtp2/smtp[2016]: 3CA964C0004: to=, relay=domain.org[XXXXXXXXX]:25, delay=2, delays=0.03/0.01/0.18/1.8,dsn=2.0.0, status=sent (250 OK id=1T86oe-0005tU-E9)Sep 2 12:50:05 myserver postfix-smtp5/smtp[2014]: 4EE244C0012: to=, relay=domain.org[XXXXXXXXX]:25, delay=2, delays=0.01/0/0.21/1.8, dsn=2.0.0, status=sent (250 OK id=1T86oe-0005tx-Gn)Sep 2 12:50:05 myserverpostfix-smtp3/smtp[2045]: 69305680035: to=, relay=domain.org[XXXXXXXXX]:25, delay=2, delays=0.05/0/0.11/1.9, dsn=2.0.0, status=sent (250 OK id=1T86oe-0005uJ-Ih)Sep 2 12:50:05 myserver postfix-smtp3/smtp[2034]: 444B94C0006: to=, relay=domain.org[XXXXXXXXX]:25,delay=2.2, delays=0.04/0/0.21/1.9, dsn=2.0.0, status=sent (250 OK id=1T86oe-0005tW-G9)Sep 2 12:50:05 myserver postfix-smtp1/smtp[2039]: 585A6583CFE: to=, relay=domain.org[XXXXXXXXX]:25, delay=2.2, delays=0.01/0/0.15/2, dsn=2.0.0, status=sent (250 OK id=1T86oe-0005u0-GO)Andalso you get an entry when the perl script is used to provide transport:Sep 2 13:24:59 myserver postfix/randomizer[2076]: Using: smtp6: Transport ServiceThis guide is based on:http://www.kutukupret.com/2011/05/22/postfix-rotating-outgoing-ip-using-tcp_table-and-perl/http://www.kutukupret.com/2010/12/06/postfix-randomizing-outgoing-ip-using-tcp_table-and-perl/Allcredists to Hari Hendaryanto