cc by-sa flurdy

How to set up a mail server on a GNU / Linux system

Step by step guide to install Postfix

Ubuntu + Postfix + Courier IMAP + MySQL + Amavisd-new + SpamAssassin + ClamAV + SASL + TLS + SquirrelMail + Postgrey

Easy to follow howto on setting up a mail server with unlimited users and domains, with IMAP/Pop access, anti-spam, anti-virus, secure authentication, encrypted traffic, web mail interface and more.

Based on an Ubuntu distribution platform, but instructions are distro generic.

postfix
8th edition
Author Ivar Abrahamsen
License: Respect (CC by-sa)
Last Update: 2009-11-25
Contact / Discuss

Notice

This document has been superseeded by a more up to date howto.

Contents

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Editions

Edition State Started Updated Description
1st Released (outdated) 2004-01 2004-02 Based on Mandrake 9.1.
2nd Released (outdated) 2004-02 2004-07 Based on Mandrake 10.x, but valid for all distributions. Very thorough. Includes package description, where to get the sources and binaries, how to build them or which RPMs to use, includes many refrences, etc etc. Starts off with a basic working server, then advances, extends and tightens it in stages.
3rd Released (outdated) 2005-05 2005-11 Based on Ubuntu 5.04, Hoary Hedgehog. More concise simplified guide to get an advanced server working quickly. Now includes SASL & TLS integration.
4th Released (outdated) 2005-10 2005-12 Based on Breezy Badger, Ubuntu 5.10. Includes Postgrey
5th Released 2006-05 2006-11 Based on Dapper Drake, Ubuntu 6.06 LTS.
6th Scrapped 2006-11 2007-10 Was to be based on Edgy Eft, Ubuntu 6.10 or 7.04. include Domain Key signing. include my mail admin or my catchall aliases admin.
7th Released 2008-04 2009-06 Updated, based on Ubuntu 8.04 LTS Hardy Heron. Using Amazon EC2 as example. (Tested with 8.10 & 9.04 as well)
8th (this) Released 2009-05 2009-11 Based on Ubuntu 8.10 (intrepid), then tested with 9.04 (jaunty) & 9.10 (karmic) as well. Using official Ubuntu ec2 as examples.
9th Next 2009-11 2009-11 Based Ubuntu 9.10 LTS (karmic) using Canonical's cloud images. Added Roundcube webmail option.
10th Early draft 2009-11 2009-11 Next version. Early testing with Ubuntu 10.04 LTS (lucid) using Canonical's cloud images.
Further details available in the change log and below in the introduction.
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Introduction

Aim

This is a step by step howto guide to set up a mail server on a GNU / Linux system. It is easy to follow, but you end up with a powerfull secure mail server.

The server accepts unlimited domains and users, and all mail can be read via your favourite clients, or via web mail.

It is secure, traffic can encrypted and it will block virtually all spam and viruses.

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Research

Dont take my word for it! Research others opinions and methods. Look at my references, look at Postfix.org's howtos, read the excellent books available (E.g. Kyle's or Hildebrandt's), search the web or read the proper documentation.

If you refer to this howto in your own document, or find useful links, then let me know.

Donate

If you found this howto very useful, spread the word and help others?

If this howto was exceptionally useful why not donate me some beer money?

Or buy a postfix book using my amazon affiliate links further down?

Or buy a t-shirt from my t-shirt shop?

Otherwise send me a Thank You note?

no fix puta
UK
kill bill
US
EU

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Software

Ubuntu
postfix
Courier IMAP
MySQL
amavisd-new
ClamAV
SpamAssassin
SquirrelMail
admin SPF
GnuPG SASL

What software packages have/will I use and why.

Please see software links appendix for further information about these software packages. In that section there is more links to documentation or forums, and viable alternatives, downloadable packages, versions details etc.

Further software and tweaks are discussed in the extension section.

Also review other peoples opinion on these packages via my references.

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Installation

Distribution

Please refer to previous edition for a discussion on distribution selection.

Base Install

With installing Ubuntu you have a choice of which base system to install. You may choose server or desktop image or very basic setups. I will assume a server install, but it should not differ.

Ps. I actually built this recent mail server using Amazon Elastic Computing Cloud (EC2). And thus I have created public images of my mail server that you can use. For more details see my EC2 section. If you have your own server, then it is not relevant.

Pss. Please note that after a while Ill stop specificying the use of sudo, as it is up to yourselves if you use it or use a priviliged user, e.g. root.

Repositories

Please refer to a previous edition for a details of repository configurations. For assitance with repositories, refer to this article on ubuntu's wiki.

Packages

You need to install a whole bunch of packages. We will install them bit by bit. But first check your package sources are correctly pointing to main multiverse restricted universe repositories of your current Ubuntu version. sudo vi /etc/apt/sources.list Secondly update your current system: sudo aptitude update sudo aptitude safe-upgrade

MySQL

First we'll install MySQL sudo aptitude install mysql-client mysql-server This will prompt you for a root password. Choose someting wise and remember it! For purpose of this tutorial I will set it to rootPASSWORD

Postfix

Then we'll install postfix sudo aptitude install postfix postfix-mysql This will prompt you to choose type of email server. Select internet site It will also suggest a server name. Correct this if needed.

SASL
sudo aptitude install libsasl2-modules-sql libgsasl7 libauthen-sasl-cyrus-perl
Courier

sudo aptitude install courier-base courier-authdaemon courier-authlib-mysql courier-imap courier-imap-ssl courier-ssl will prompt you about webdirectories. You can say no to this. It will also warn you about the certificate location. Ignore it.

ClamAV

sudo aptitude install clamav-base libclamav6 clamav-daemon clamav-freshclam (Earlier vesions of Ubuntu may use libclamav5)

Amavis, SpamAssassin, postgrey

sudo aptitude install amavisd-new sudo aptitude install spamassassin spamc sudo aptitude install postgrey

SquirrelMail
sudo aptitude install squirrelmail squirrelmail-locales php-pear php5-cli

phpMyAdmin
sudo aptitude install phpmyadmin

Accept apache2 as the web server.

ShoreWall
sudo aptitude install shorewall-common shorewall-perl # for earlier ubuntu versions use package shorewall instead sudo aptitude install shorewall shorewall-doc

Amazon provides a firewall/ access control for its servers, so not always needed then, but nice to have. And in all others situations; a must have.

Extras

I also install a few other packages that I personally prefer. But nothing todo with the mail server. sudo aptitude install vim mutt lynx

Package status

To find out which packages you may have installed, you can use for example: sudo dpkg --list | grep postfix or sudo aptitude search postfix

EC2 Bundle

My AMI flurdy-amis/ubuntu-mail-server-clean is based on Canonical's official Ubuntu with these basic mail server packages installed.

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Configuration

Simple mail server

Now lets configure a simple mail server using some of the packages installed.

Firewall

Shorewall

Not essential for an EC2 image. It is essential for a normal server. UFW is bundled with recent Ubuntu distributions, but I still prefer Shorewall for servers.

Basically at first you want to only allow SSH. Then SMTP and IMAP from your IP only.

When you are confident that the mail server is secure, you can open SMTP to the world. If you prefer you can also open IMAP to the world, unless you have a very small client IP range.

Later you may open web access to the webmail and admin gui. This you may also restrict to specific IPs.

SSH only

By default Shorewall in Ubuntu has an empty set up. You can find the default values for Shorewall in /usr/share/doc/shorwall-common/default-config. And examples in /usr/share/doc/shorwall-common/examples. We will create a basic set up.

First configure which network adapters we are accessing the net. cp /usr/share/doc/shorewall-common/default-config/interfaces /etc/shorewall/ vi /etc/shorewall/interfaces net eth0 detect dhcp,tcpflags,logmartians,nosmurfs

Then we will configure network zones cp /usr/share/doc/shorewall-common/default-config/zones /etc/shorewall/ vi /etc/shorewall/zones Add the firewall if not there and the internet as a zone. fw firewall # loc ipv4 net ipv4

Then if needed to specify hosts you can do it in this file. E.g. If you wanto specify what is your home IP etc. cp /usr/share/doc/shorewall-common/default-config/hosts /etc/shorewall/ vi /etc/shorewall/hosts # loc eth0:192.168.0.0/24

Then set what is the default policy for firewall access. cp /usr/share/doc/shorewall-common/default-config/policy /etc/shorewall/ vi /etc/shorewall/policy $FW net ACCEPT net $FW DROP info net all DROP info # The FOLLOWING POLICY MUST BE LAST all all REJECT info

For safety in case it goes down. cp /usr/share/doc/shorewall-common/default-config/routestopped /etc/shorewall/ vi /etc/shorewall/routestopped eth0 0.0.0.0 routeback You may put in a netmask of your ip range if you are more concerned.

Now for the main firewall rules. You can find predetermined macro rules for Shorewall in /usr/share/shorewall. cp /usr/share/doc/shorewall-common/default-config/rules /etc/shorewall/ vi /etc/shorewall/rules SSH/ACCEPT net $FW

Open for business

Once your server is working come back to this step and open up SMTP and Web access to others.

vi /etc/shorewall/rules Ping/ACCEPT net $FW # Permit all ICMP traffic FROM the firewall TO the net zone ACCEPT $FW net icmp # mail lines SMTP/ACCEPT net $FW SMTPS/ACCEPT net $FW Submission/ACCEPT net $FW IMAP/ACCEPT net $FW IMAPS/ACCEPT net $FW #web Web/ACCEPT net $FW

Firewall configuring is always risky business, as it is easy to lock yourself out. To test the setup syntax, run shorewall check Restart it with /etc/init.d/shorewall restart

Then to switch it on during boot: vi /etc/default/shorewall startup=1

For more details on IP Tables and Shorewall, look up its website.

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MTA

Postfix

You should put the name of your server in this file sudo vi /etc/mailname Could be something like smtp.domain.name, where domain name obviously is replaced with your domain name.

Now will open the main postfix configuration file: sudo vi /etc/postfix/main.cf Debian and Ubuntu already puts in some sensible default values in this file. You may need to comment some of them out if we put the same in as well.

First specify the name of your server. # This is already done in /etc/mailname #myhostname= mail.example.com Next is the origin which is the domain appended to email from this machine, this can be your full servername, or domain name. # myorigin=/etc/mailname myorigin=example.com

Then decide what the greeting text will be. Enough info so it is useful, but not divelge everything to potential hackers. smtpd_banner = $myhostname ESMTP $mail_name

Next you need to decide whether to send all outgoing mail via another SMTP server, or send them yourself. I send via my ISP's server, so it has to worry about the queing etc. If you send it yourself then you are not reliant on 3rd party server. But you may risk more exposure and accidentally be blocked by spam blockers. And it is more work for your server. Also many servers block dynamic dns hosts, so you may find your server gets rejected. However choose whichever you are comfortable with. # leave blank to do it yourself relayhost =# or put it an accessible smtp server relayhost = smtp.yourisp.com

Next is network details. You will accept connection from anywhere, and you only trust this machine inet_interfaces = all mynetworks_style = host

Next you can masquerade some outgoing addresses. Say your machine's name is mail.domain.com. You may not want outgoing mail to come from username@mail.example.com, as you'd prefer username@example.com. You can also state which domain not to masquerade. E.g. if you use a dynamic dns service, then your server address will be a subdomain. You can also specify which users not to masquerade. # masquerade_domains = mail.example.com www.example.com !sub.dyndomain.com # masquerade_exceptions = root

As we will be using virtual domains, these need to be empty. local_recipient_maps = mydestination =

Then will set a few numbers. # how long if undelivered before sending warning update to sender delay_warning_time = 4h # will it be a permanent error or temporary unknown_local_recipient_reject_code = 450 # how long to keep message on queue before return as failed. # some have 3 days, I have 16 days as I am backup server for some people # whom go on holiday with their server switched off. maximal_queue_lifetime = 7d # max and min time in seconds between retries if connection failed minimal_backoff_time = 1000s maximal_backoff_time = 8000s # how long to wait when servers connect before receiving rest of data smtp_helo_timeout = 60s # how many address can be used in one message. # effective stopper to mass spammers, accidental copy in whole address list # but may restrict intentional mail shots. smtpd_recipient_limit = 16 # how many error before back off. smtpd_soft_error_limit = 3 # how many max errors before blocking it. smtpd_hard_error_limit = 12

Now we can specify some restrictions. Be carefull that each setting is on one line only. # Requirements for the HELO statement smtpd_helo_restrictions = permit_mynetworks, warn_if_reject reject_non_fqdn_hostname, reject_invalid_hostname, permit # Requirements for the sender details smtpd_sender_restrictions = permit_mynetworks, warn_if_reject reject_non_fqdn_sender, reject_unknown_sender_domain, reject_unauth_pipelining, permit # Requirements for the connecting server smtpd_client_restrictions = reject_rbl_client sbl.spamhaus.org, reject_rbl_client blackholes.easynet.nl, reject_rbl_client dnsbl.njabl.org # Requirement for the recipient address smtpd_recipient_restrictions = reject_unauth_pipelining, permit_mynetworks, reject_non_fqdn_recipient, reject_unknown_recipient_domain, reject_unauth_destination, permit smtpd_data_restrictions = reject_unauth_pipelining

Further restrictions: # require proper helo at connections smtpd_helo_required = yes # waste spammers time before rejecting them smtpd_delay_reject = yes disable_vrfy_command = yes

Next we need to set some maps and lookups for the virtual domains. # not sure of the difference of the next two # but they are needed for local aliasing alias_maps = hash:/etc/postfix/aliases alias_database = hash:/etc/postfix/aliases # this specifies where the virtual mailbox folders will be located virtual_mailbox_base = /var/spool/mail/virtual # this is for the mailbox location for each user virtual_mailbox_maps = mysql:/etc/postfix/mysql_mailbox.cf # and their user id virtual_uid_maps = mysql:/etc/postfix/mysql_uid.cf # and group id virtual_gid_maps = mysql:/etc/postfix/mysql_gid.cf # and this is for aliases virtual_alias_maps = mysql:/etc/postfix/mysql_alias.cf # and this is for domain lookups virtual_mailbox_domains = mysql:/etc/postfix/mysql_domains.cf # this is how to connect to the domains (all virtual, but the option is there) # not used yet # transport_maps = mysql:/etc/postfix/mysql_transport.cf

You need to set up an alias file. This is only used locally, and not by your own mail domains. sudo cp /etc/aliases /etc/postfix/aliases # may want to view the file to check if ok. # especially that the final alias, eg root goes # to a real person sudo postalias /etc/postfix/aliases

Next you need to set up the folder where the virtual mail will be stored. This may have already been done by the apt-get. And also create the user whom will own the folders. # to add if there is not a virtual user sudo mkdir /var/spool/mail/virtual sudo groupadd virtual -g 5000 sudo useradd virtual -u 5000 -g 5000 sudo chown -R virtual:virtual /var/spool/mail/virtual

Note: If using Amazon ec2 you may want to move the mail spool to /mnt or an EBS location. You will need to symlink correctly afterwards.

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Postfix's MySQL configuration

Next we need to set up the files to access the lookups via the database. We will only set up a few now, and the rest later when/if needed:

Edit(create) how to find the users mailbox location sudo vi /etc/postfix/mysql_mailbox.cf

user=mail password=mailPASSWORD dbname=maildb table=users select_field=maildir where_field=id hosts=127.0.0.1 additional_conditions = and enabled = 1

Create how to find the user id (this step I will eventualy remove) sudo vi /etc/postfix/mysql_uid.cf

user=mail password=mailPASSWORD dbname=maildb table=users select_field=uid where_field=id hosts=127.0.0.1

Create how to find the group id. (this step I will eventualy remove) sudo vi /etc/postfix/mysql_gid.cf

user=mail password=mailPASSWORD dbname=maildb table=users select_field=gid where_field=id hosts=127.0.0.1

Create how to find the email alias: sudo vi /etc/postfix/mysql_alias.cf

user=mail password=mailPASSWORD dbname=maildb table=aliases select_field=destination where_field=mail hosts=127.0.0.1 additional_conditions = and enabled = 1

Create how to find the domains: sudo vi /etc/postfix/mysql_domains.cf

user=mail password=mailPASSWORD dbname=maildb table=domains select_field=domain where_field=domain hosts=127.0.0.1 additional_conditions = and enabled = 1

As you can see the 3 first are very similar, only the select_field changes. If you specify an ip in hosts, (as opposed to 'localhost') then it will communicate over tcp and not the mysql socket. (chroot restriction). Actually you can avoid using separate uid and guid files as those details are the same for all, but I do anyway. Ps. remember to replace the password with your chosen mail user password.

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No LOL


Database

MySQL

Now we will need to create the tables for thos lookups just specified. First you need to create a user to use in MySQL for mail only. Then you need to create the database, Take note of your chosen mail username and password. You will need the password you specified for root during MySQL package installation.

# If not already done (in package installation)... mysqladmin -u root password new_password # log in as root mysql -u root -p # then enter password for the root account when prompted Enter password: # then we create the mail database create database maildb; # then we create a new user: "mail" GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP ON maildb.* TO 'mail'@'localhost' IDENTIFIED by 'mailPASSWORD'; GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP ON maildb.* TO 'mail'@'%' IDENTIFIED by 'mailPASSWORD'; exit; Obviously replace mailPASSWORD with your chosen password!

Then you will need to create these tables:

We will create more later on for further extensions, but only these are relevant now.

Log in to mysql as the new mail user mysql -u mail -p maildb # enter the newly created password Enter password:

Then run this commands to create the tables:

CREATE TABLE `aliases` ( `pkid` smallint(3) NOT NULL auto_increment, `mail` varchar(120) NOT NULL default '', `destination` varchar(120) NOT NULL default '', `enabled` tinyint(1) NOT NULL default '1', PRIMARY KEY (`pkid`), UNIQUE KEY `mail` (`mail`) ) ; CREATE TABLE `domains` ( `pkid` smallint(6) NOT NULL auto_increment, `domain` varchar(120) NOT NULL default '', `transport` varchar(120) NOT NULL default 'virtual:', `enabled` tinyint(1) NOT NULL default '1', PRIMARY KEY (`pkid`) ) ; CREATE TABLE `users` ( `id` varchar(128) NOT NULL default '', `name` varchar(128) NOT NULL default '', `uid` smallint(5) unsigned NOT NULL default '5000', `gid` smallint(5) unsigned NOT NULL default '5000', `home` varchar(255) NOT NULL default '/var/spool/mail/virtual', `maildir` varchar(255) NOT NULL default 'blah/', `enabled` tinyint(3) unsigned NOT NULL default '1', `change_password` tinyint(3) unsigned NOT NULL default '1', `clear` varchar(128) NOT NULL default 'ChangeMe', `crypt` varchar(128) NOT NULL default 'sdtrusfX0Jj66', `quota` varchar(255) NOT NULL default '', `procmailrc` varchar(128) NOT NULL default '', `spamassassinrc` varchar(128) NOT NULL default '', PRIMARY KEY (`id`), UNIQUE KEY `id` (`id`) ) ;

The last few fields in the users table are not required, but useful if you extend later.

# To visualise the tables created: describe aliases; describe domains; describe users; # then quit mysql exit;

Next is to edit the MySQL's my.cnf file. In Ubuntu/debian this is created by default. In Mandrake I had to manually create a blank one in /etc. But we need to configure it, so: sudo vi /etc/mysql/my.cnf In previous version you needed to comment out this line #skip-networking However in todays file the default is to bind the address to localhost, which is fine. bind-address = 127.0.0.1 It is very useful at the start to log any SQL calls that makes it to MySQL. So enable this line: log = /var/log/mysql/mysql.log Then in a few weeks comment it out when everything is working, as it slows mysql down

Restart MySQL to make sure its picking up the new settings. sudo /etc/init.d/mysql restart

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Pop/IMAP

Courier IMAP

Please refer to previous edition for more explanations. But below is the details of what you need to change.

sudo vi /etc/courier/authdaemonrc Change to mysql mode. authmodulelist="authmysql" Further down enable logging. DEBUG_LOGIN=2

sudo vi /etc/courier/authmysqlrc Changed user MYSQL_USERNAME mail Changed password to whichever you have chosen MYSQL_PASSWORD mailPASSWORD Changed database MYSQL_DATABASE maildb Changed users table MYSQL_USER_TABLE users Keep commented in crypt pw MYSQL_CRYPT_PWFIELD crypt Keep commented out clear pw # MYSQL_CLEAR_PWFIELD clear Added maildir MYSQL_MAILDIR_FIELD concat(home,'/',maildir) Added where clause MYSQL_WHERE_CLAUSE enabled=1

Lastly you can have a look at the imapd file, but no changes is needed. vi /etc/courier/imapd

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Summary

You now have a basic mail server!

Before continuing to the advanced and secure mail server you must ensure the basic setup works. This will save you from loads of pain further on.
It is very easy to make typos, miss tiny steps, unclear steps or simple actual errors in this howto.

Ive created an EC2 bundle for this stage: flurdy-amis/ubuntu-mail-server-simple.

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wrong evolution
Somewhere, something went terribly wrong

Advanced mail server

Now lets extend this setup with more useful content checks , security and user interfaces.

Content Checks (Anti spam & anti virus)

Amavisd-new

Amavisd ties together all the different ways of checking email content for spam and viruses.

The defaults are pretty good and also the ubuntu documentation is pretty clear, and recommended.

Here is a tweaked version of it:

Initially we will not enable spam or virus detection! This is so we can get amavis set up to receive, check and pass on emails before we go on and over-complicate it.

All of amavis' configuration files are in /etc/amavisd. They are now spread across several files in conf.d. Debian and Ubuntu defaults are now very sensible and spread into seperate files. cd /etc/amavis/conf.d

01-debian defaults are fine.

Have a look at less 05-domain_id but dont change anything in it.

Have a look at less 05-node_id but dont change anything in it.

Have a look at less 15-av_scanners but dont change anything in it.

Edit content check file sudo vi 15-content_filter_mode Comment out both virus and spam scans. (Default). # #@bypass_virus_checks_maps = ( # \%bypass_virus_checks, \@bypass_virus_checks_acl, \$bypass_virus_checks_re); # @bypass_spam_checks_maps = ( # \%bypass_spam_checks, \@bypass_spam_checks_acl, \$bypass_spam_checks_re);

Have a look at less 20-debian_defaults but dont change anything in it.

25-amavis_helpers defaults are fine.

30-template-localization defaults are fine.

Edit user file sudo vi 50-user In the middle insert: @local_domains_acl = qw(.); $log_level = 2; $syslog_priority = 'debug'; $sa_kill_level_deflt = 8.0; # triggers spam evasive actions $final_spam_destiny = D_PASS; # $final_spam_destiny = D_DISCARD;

We have not setup amavis to scan and pass along incomming email. Next we will setup postfix to talk to amavis.

vi /etc/postfix/master.cf Append these lines to the end of the file (make sure they are not already present). (Note the -o lines have spaces in front of them. amavis unix - - - - 2 smtp -o smtp_data_done_timeout=1200 -o smtp_send_xforward_command=yes -o disable_dns_lookups=yes -o max_use=20 127.0.0.1:10025 inet n - - - - smtpd -o content_filter= -o local_recipient_maps= -o relay_recipient_maps= -o smtpd_restriction_classes= -o smtpd_delay_reject=no -o smtpd_client_restrictions=permit_mynetworks,reject -o smtpd_helo_restrictions= -o smtpd_sender_restrictions= -o smtpd_recipient_restrictions=permit_mynetworks,reject -o smtpd_data_restrictions=reject_unauth_pipelining -o smtpd_end_of_data_restrictions= -o mynetworks=127.0.0.0/8 -o smtpd_error_sleep_time=0 -o smtpd_soft_error_limit=1001 -o smtpd_hard_error_limit=1000 -o smtpd_client_connection_count_limit=0 -o smtpd_client_connection_rate_limit=0 -o receive_override_options=no_header_body_checks,no_unknown_recipient_checks Also add the following two lines immediately below the "pickup" transport service: -o content_filter= -o receive_override_options=no_header_body_checks

and then added to main.cf sudo vi /etc/postfix/main.cf content_filter = amavis:[127.0.0.1]:10024

Enable scanning by ClamAV of amavis' temporary files. sudo adduser clamav amavis

This should be it to get amavis working. If emails are picked up by amavis and passed back to postfix then it looks okay. Next is to uncomment the anti virus and anti spam lines in sudo vi 15-content_filter_mode @bypass_virus_checks_maps = ( \%bypass_virus_checks, \@bypass_virus_checks_acl, \$bypass_virus_checks_re); @bypass_spam_checks_maps = ( \%bypass_spam_checks, \@bypass_spam_checks_acl, \$bypass_spam_checks_re); But do that after the next section (SpamAssassin).

When things are working we will turn down logging level, and start bouncing/discarding spam. sudo vi /etc/amavis/conf.d/50-user @local_domains_acl = qw(.); $log_level = 1; $syslog_priority = 'info'; $sa_kill_level_deflt = 8.0; # triggers spam evasive actions #$final_spam_destiny = D_PASS; $final_spam_destiny = D_DISCARD;

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Anti-Spam

SpamAssassin

The default config of spam assassin is okay. You could refer to previous edition for more configuration options.

You do need to tell SpamAssassin to start smapd on boot. vi /etc/default/spamassassin ENABLED=1

One configuration option you could tweak is to enable Bayes and auto learning. vi /etc/spamassassin/local.rf

I read your email
I read your email
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Anti Virus

ClamAV

ClamAV does not need setting up. Configuration files are in /etc/clamav, but they are automatically generated, so do not edit.

By default freshclam, the daemon that updates the virus definition database, is run 24 times a day. That seems a little excessive, so I tend to set that to once a day. sudo dpkg-reconfigure clamav-freshclam It will also ask if you want it to be daemon (yes) and which server is closest to you.

If needed, the command below will redefine the configuration with a lot of questions. Not needed unless you need to configure. sudo dpkg-reconfigure clamav-base

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Postgrey

The default config of postgrey is okay. However you need to tell Postfix to use it. sudo vi /etc/postfix/main.cf And then edit the recipient restrictions: smtpd_recipient_restrictions = reject_unauth_pipelining, permit_mynetworks, permit_sasl_authenticated, reject_non_fqdn_recipient, reject_unknown_recipient_domain, reject_unauth_destination, check_policy_service inet:127.0.0.1:10023, permit

You can tweak whitelisting in /etc/postgrey. You can tweak postgrey configuration by tweaking /etc/default/postgrey. E.g. delay, auto whitelisting, or reject message.

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You know have an advanced mail server. You can use this, but Id recommend continuing. However this is a good point to test the set up so far and to insert some data in the db.

Ive created an EC2 bundle for this stage: flurdy-amis/ubuntu-mail-server-spam.

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no, i will not fix your computer
No, I will not fix your computer

Secure mail server

Stopping hackers, phishers, spammers, your boss and your neighbour from accessing your server or the traffic in between is important, and easily done.

Authentication

Normal email traffic between clients and servers are in open plain text. That includes passwords and content of emails.

SASL

SASL secures the actual authentication (login), by encoding the passwords so that it can not be easily intercepted. The rest of the emails are however in clear plain text.

This is a section I will revisit for the next edition! Meanwhile please refer to previous edition for more detail.

Encryption

TLS

Encrypting the traffic stops anyone else listening in on your email communications. And is very recommended. There are different types of communication to encrypt: The data traffic between your email applications and the server when you read emails or when you send emails, and communication between other email servers and your server.

For the encryption of reading emails, it is Courier you need to configure. For sending, and beetwen server encryption it is Postfix.

TLS in Postfix

To encrypt you need certificates. Ubuntu creates some for you for which you can use while setting up the server. However before you go live, it is recommended to create your own with your proper domain name etc. Please refer to previous edition for more detail.

vi /etc/postfix/main.cf There are already some TLS settings in the default debian/ubuntu version of this file. I moved these to the end, for clarity, but that is up to you. # TLS parameters #smtp_use_tls = no smtp_tls_security_level = may #smtpd_use_tls=yes smtpd_tls_security_level = may #smtpd_tls_auth_only = no smtp_tls_note_starttls_offer = yes smtpd_tls_loglevel = 1 smtpd_tls_received_header = yes smtpd_tls_session_cache_timeout = 3600s tls_random_source = dev:/dev/urandom smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key #smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache #smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

Next we have a look at the master.cf file. vi /etc/postfix/master.cf By default only the normal smtp service is enabled, which is fine. But I prefer to enable submission (port 587), so that clients can use it, and I can restrict them to TLS only. Also enabled smtps service (port 465), for some compatebility with some older clients (outlook express etc).

submission inet n - n - - smtpd -o smtpd_sasl_auth_enable=yes # if you do not want to restrict it encryption only, comment out next line -o smtpd_tls_auth_only=yes # -o smtpd_tls_security_level=encrypt # -o header_checks= # -o body_checks= -o smtpd_client_restrictions=permit_sasl_authenticated,reject_unauth_destination,reject -o smtpd_sasl_security_options=noanonymous,noplaintext -o smtpd_sasl_tls_security_options=noanonymous # -o milter_macro_daemon_name=ORIGINATING smtps inet n - - - - smtpd -o smtpd_tls_wrappermode=yes -o smtpd_sasl_auth_enable=yes -o smtpd_tls_auth_only=yes -o smtpd_client_restrictions=permit_sasl_authenticated,reject -o smtpd_sasl_security_options=noanonymous,noplaintext -o smtpd_sasl_tls_security_options=noanonymous # -o milter_macro_daemon_name=ORIGINATING
TLS in Courier

Again Ubuntu has created a certificate for you, but if you want to create your own, especially for a properly named server, then do this. cd /etc/courier openssl req -x509 -newkey rsa:1024 -keyout imapd.pem \ -out imapd.pem -nodes -days 999 For more details review last edition.

Then you need to edit vi /etc/courier/imapd-ssl By default Ubuntu already points to you certificate TLS_CERTFILE=/etc/courier/imapd.pem Modify this if needed.

Also you if want to restrict IMAP users to SSL/TLS only toggle this setting to 1. IMAP_TLS_REQUIRED=1



For maximum compatability it is not wise to restrict to TLS only for the traffic between servers. As this means not all valid emails sent by others can reach your server. However enabling them the option to encrypt is a good idea.

Be aware that the emails are not encrypted on your machine, nor on the server. For this type of client encryption, please refer to previous edition for more on GnuPG.

In some situations SASL and TLS do not play well together. Those situations are in combinations of storing encrypted passwords, using MD5 authentication over encrypted traffic. I recommend, insisting on TLS traffic with your authenticating clients, which then negates the need for SASL.

You know have an advanced secure mail server. Now is another good point to test the set up so far and to insert some data in the db.

Ive created an EC2 bundle for this stage: flurdy-amis/ubuntu-mail-server-secure.

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Webmail

Using among others the https://help.ubuntu.com/community/Squirrelmail as an updated reference.

Enable web access

You may need to enable web access in the firewall. Check the firewall configuration if this neccessary.

You need to copy a SquirrelMail configuration to apache. sudo cp /etc/squirrelmail/apache.conf /etc/apache2/sites-available/squirrelmail And enable with this: sudo ln -s /etc/apache2/sites-available/squirrelmail /etc/apache2/sites-enabled/500-squirrelmail Or as Florent recommends, use: sudo a2ensite squirrelmail

You may accept the default apache configuration where squirrelmail is folder in all sites. But I prefer virtual hosting. But you dont need to do these next steps. sudo vi /etc/apache2/sites-available/squirrelmail Comment out the alias. # alias /squirrelmail /usr/share/squirrelmail Uncomment the virtual settings., and insert your servers name. # users will prefer a simple URL like http://webmail.example.com DocumentRoot /usr/share/squirrelmail ServerName webmail.example.com If you have apache SSL enabled in apache, then you can also uncomment the mod_rewrite section for further security.

Reload apache to activate changes. First test if ok. sudo apache2ctl -t Then reload it. sudo /etc/init.d/apache2 reload

You can now go toyourdomain.com/squirrelmail/ or mail.yourdomain.com if you chose virtual host. This should show a squirrel mail page. Log in wont work yet though.

Start configuring squirrel mail.
sudo squirrelmail-configure

Initially change nothing. You can customize more afterwards. You can browse, and exit sub menues by typing R.

Type 2 to edit server settings. Type A to edit IMAP settings.

Type 8 to edit server software. Enter courier. courier

Now they say using TLS over localhost is a waste of time. But I do anyway. Type 7 to edit secure IMAP. Type Y to enable it.

Type 5 to edit IMAP port. Enter 993

Type S to save your changes. Hit Enter.

Type Q to exit.

You can now go to yourdomain.com/squirrelmail/ or mail.yourdomain.com if you chose virtual host. This should show a squirrel mail page. Log in will now work. (Except you may not have defined users, check data section. And they may not have received an email which also means you can not view any IMAP info.)

Please refer to previous edition for more detail. E.g. creating address books and user preferences.

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Administration

Enable web access

You may need to enable web access in the firewall. Check the firewall configuration if this neccessary.

You need to copy a phpMyAdmin configuration to apache. sudo cp /etc/phpmyadmin/apache.conf /etc/apache2/sites-available/phpmyadmin And enable with this: sudo ln -s /etc/apache2/sites-available/phpmyadmin /etc/apache2/sites-enabled/400-phpmyadmin Or as Florent recommends, use: sudo a2ensite phpmyadmin

You may choose to restrict phpMyAdmin to a spefic virtual host. If so you need to, edit sudo vi /etc/apache2/sites-available/phpmyadmin and comment out the alias. And insert the alias into a virtual host configuration. For this example we are not.

Reload apache to activate changes. First test if ok. sudo apache2ctl -t Then reload it. sudo /etc/init.d/apache2 reload

You can now go to http://yourdomain.com/phpmyadmin/, and login with the mail user. You can use it as it is, but I recommend securing it a bit more.

One simple way is adding apache's .htaccess login requirement.

Further restrictions can be restricting to a specific virtual host. Or renaming the folder. Purely ubfuscating, but simple.

Or using the example in the webmail section, and adding SSL requirement to the connection. Or disabel mysql root's access via phpMyAdmin.

Please refer to previous edition for example on htaccess, and mysql user restriction.

You know have a finished mail server. This is as far as the main guide goes. Hope it was clear enough to follow.

Now it is time to insert data, and to test how it works.

Feel free to extend it with my suggestions further down.

Ive created an EC2 bundle for this stage: flurdy-amis/ubuntu-mail-server-webmail.

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Data

Add users and domains

So we got a fully set up mail server... Well no, there is no users, domains, no nothing!

Okay, first you need add some default data, some which are required, some which make sense.

Then we'll add your own users and domains.

Required domains and users

First the required domains for local mail

# Use phpMyAdmin or command line mysql INSERT INTO domains (domain) VALUES ('localhost'), ('localhost.localdomain');

Then some default aliases. Some people say these are not needed, but I'd include them.

INSERT INTO aliases (mail,destination) VALUES ('postmaster@localhost','root@localhost'), ('sysadmin@localhost','root@localhost'), ('webmaster@localhost','root@localhost'), ('abuse@localhost','root@localhost'), ('root@localhost','root@localhost'), ('@localhost','root@localhost'), ('@localhost.localdomain','@localhost');

Then a root user.

INSERT INTO users (id,name,maildir,crypt) VALUES ('root@localhost','root','root/', encrypt('apassword') );
I see dumb people

Domains and users

Now lets add some proper data.

Say you want this machine to handle data for the fictional domains of "blobber.org", "whopper.nu" and "lala.com".

Then say this machine's name is "mail.blobber.org".

All email to lala.com is to be forwarded to whupper.nu.

INSERT INTO domains (domain) VALUES ('blobber.org'), ('mail.blobber.org'), ('whopper.nu'), ('lala.com'); INSERT INTO aliases (mail,destination) VALUES ('@lala.com','@whupper.nu'), ('@mail.blobber.org','@blobber.org'), ('postmaster@whopper.nu','postmaster@localhost'), ('abuse@whopper.nu','abuse@localhost'), ('postmaster@blobber.org','postmaster@localhost'), ('abuse@blobber.org','abuse@localhost');

You also have two users called "Xandros" and "Vivita".

INSERT INTO users (id,name,maildir,crypt) VALUES ('xandros@blobber.org','xandros','xandros/', encrypt('apassword') ), ('vivita@blobber.org','vivita','vivita/', encrypt('anotherpassword') ); INSERT INTO aliases (mail,destination) VALUES ('xandros@blobber.org','xandros@blobber.org'), ('vivita@blobber.org','vivita@blobber.org');

You want all mail for whooper.nu to go to xandros (catchall).

INSERT INTO aliases (mail,destination) VALUES ('@whopper.nu','xandros@blobber.org');

There is also a "Karl" user, but he does want all mail forwarded to an external account.

INSERT INTO aliases (mail,destination) VALUES ('karl@blobber.org','karl.vovianda@gmail.com');

So what does each of these lines actually do? Well the domains are pretty straight forward.

The users are as well, it requires four fields. ID is the email address of the user, and also its username when loggin in, described later on. NAME is optional description of the user. MAILDIR is the name of the folder inside /var/spool/mail/virtual. It must end in a /, otherwise it wont be used as a unix maildir format. CRYPT is the encrypted text password to use.

The alises are the interesting part. Lets start from a top down view to see how emails get delivered:

Say an email arrives addressed to "john@whopper.nu".

Lets try "julian.whippit@lala.com".

Any mail arriving for "karl@blobber.org" or "karl@lala.com", gets forward to an external address of "karl.vovianda@gmail.com". So forwarding is simple. I tend to use a subdomain for all my friends addresses as easily I forget what their real addresses are, and I use different email clients all the time.

I also added the required aliases of postmaster and abuse to blobber.org and whopper.nu. The catchall for lala.com means they are not required for that domain.
Another useful alias to add is root, as often you get admin mail from e.g cron jobs within those domains etc. Other often used aliases are info, sysadmin, support, sales, webmaster, mail, contact and all. But they are also honeypots for spam, so just include the ones you think you will need.

Adding template

So to add a new domain to the system, You do this, replacing the italics with relevant data:

INSERT INTO domains (domain) VALUES ('domain.tld'); INSERT INTO aliases (mail,destination) VALUES ('@domain.tld','email@address'), ('postmaster@domain.tld','email@address'), ('abuse@domain.tld','email@address');

And to add a new user to the system, do this:

INSERT INTO users (id,name,maildir,clear) VALUES ('email@address','short description','foldername/',encrypt('password')); INSERT INTO aliases (mail,destination) VALUES ('email@address','email@address');
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Common SQL

A selection of useful sql statements, if you are not using an admin/manager program to maintain your email domains and users.

Find domains without a catchall

#Remember some might be disabled SELECT dom.domain FROM domains dom LEFT JOIN aliases al ON CONCAT( '@', dom.domain ) = al.mail WHERE al.mail is null OR al.enabled = 0 ORDER BY dom.domain ASC

Find aliases for an invalid domain

SELECT al.* FROM aliases al LEFT JOIN domains dom ON dom.domain = SUBSTRING(al.mail,LOCATE('@',al.mail)+1) WHERE dom.domain is null OR dom.enabled = 0 ORDER BY al.mail ASC

Find all non local destination aliases

SELECT al.* FROM aliases al LEFT JOIN domains dom ON dom.domain = SUBSTRING(al.destination,LOCATE('@',al.destination)+1) WHERE dom.domain is null ORDER BY al.enabled, al.destination ASC, al.mail ASC

Find all aliases for a certain domain

SELECT al.* FROM aliases al WHERE SUBSTRING(al.mail,LOCATE('@',al.mail)+1) = 'domain.tld' ORDER BY al.enabled, al.mail ASC

Find all aliases for a certain domains, checking if enabled for both domain and alias

select * from domains d join aliases a on a.mail like concat( '%','@',d.domain) and a.enabled = 1 where d.enabled = 1 and d.domain like '%foobar%' order by d.domain,a.mail
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Test

Please refer to the previous edition for how to test your setup. That edition have an extensive testing section. It actually has two test sections!

So time to tail, tail and tail again the mail.log and mysql.log. Which is always a good think to do now and again even after you got it working. As you can quickly see potential new problems.

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Intialize

Brief hints if you receive a ready setup machine (or EC2 AMI), and what then to check and to customize it to your setup.

Stop services

First stop services so they wont accidentally do something. sudo /etc/init.d/postfix stop sudo /etc/init.d/courier-imap-ssl stop sudo /etc/init.d/courier-imap stop sudo /etc/init.d/courier-authdaemon stop sudo /etc/init.d/mysql stop sudo /etc/init.d/amavisd stop sudo /etc/init.d/spamassassin stop sudo /etc/init.d/clamav stop

Restrict firewall

Check what the firewall rules are. vi /etc/shorewall/rules Refer to the . Restrict to just SSH access for now.

Change passwords

Next the passwords needs to be changed. For both the system and mysql.

System passwords

Check which users are defined on the system. cat /etc/passwd Apart from all the system ones, there should probably be none (if EC2 AMI) or just your user if it is a standard Ubuntu install. If there are some users, you need to change their passwords.

SSH Access

Next we check whom got SSH access. If there was any users defined, check their home folders for ssh keys. cat /home/username/.ssh/auth* Remove any you do not expect to be there. Next check if and which specific users has been defined for SSH access in vi /etc/ssh/sshd Usually this is fine.

MySQL passwords

First you need to change the root mysql user. If none has been set do this mysqladmin -u root password new_password Otherwise do this and you will be prompted for the old password mysqladmin -u root password new_password -p

Then the default mail user as well. If you know the old password mysqladmin -u mail password new_password -p Otherwise log into mysql as root: mysql -u root -p Enter new root password specified above, then: update mysql.user set password=password('apassword') where user='mail'; flush privileges; You may need to revisit the top of MySQL section to re-grant the mail use rights on the database.

If you do not know the old root password, you have to restart mysql without grant rights. Google it... :)

Update postfix mysql configuration files with the new password. sudo vi /etc/postfix/mysql* password=apassword Update courier's authmysql file with the new password as well. sudo vi /etc/courier/authmysqlrc MYSQL_PASSWORD apassword

Check configurations

You should scan the postfix, courier, etc. configurations to check if they match what you expect.

Set machine name

Now you need to define your machine name, e.g. something like smtp.yourdomain.com. You need to define it in sudo vi /etc/mailname And then your domain name in sudo vi /etc/postfix/main.cf under the mydomain setting myorigin=yourdomain.com It could also be smart to check what the unix hostname is specified as hostname This can be reset by sudo hostname smtp.yourdomain.com. All though this does not have to be the same as your postfix mail server name. You may want to speficiy some hosts in hosts file as well, sudo vi /etc/hosts 127.0.0.1 localhost.localdomain localhost 127.0.0.1 smtp.yourdomain.com smtp

Certificates

You could go along with the generated certificates (if they are there, default for Ubuntu). Or if you could create new ones with the correct machine name in them. Especially if this a mail server used by many, and authenticiy is important. Follow the TLS certificate instructions for Postfix and Courier.

Start and test services.

Next you need to start your mail services and test them. sudo /etc/init.d/mysql start sudo /etc/init.d/spamassassin start sudo /etc/init.d/clamav start sudo /etc/init.d/amavisd start sudo /etc/init.d/postfix start sudo /etc/init.d/courier-imap-ssl start sudo /etc/init.d/courier-imap start sudo /etc/init.d/courier-authdaemon start

So test tjenestene via testing section.

Insert data

Insert your mail domains, aliases and users using the data section.

Some times there are test data already in the database. Remove them. E.g.; mysql -u mail -papassword maildb delete from domains where domain = 'bar.com'; delete from aliases where mail = 'foo@bar.com';

Open firewall

Then open up the firewall, follow the world access bit in the firewall configuration. Voila. Up and running. Well we hope.

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Extend

Kill Bill

Please refer to previous edition for how and why you can extend this mail server.

By now you should have a fully working system. No point extending and complicating it untill then. What next? There are many ways to extend the server, to create your own powerfull customized version.

Some of these sections can be brief as they are not core to this howto.

Remote MX mail backup

With MX backup loosing emails are unlikely.

Normally if someone sends an email destined for you, their server will try and connect to your server. If it can't reach your server for whatever reason ( it is down, dns issues, there is network problems, or just too busy ), the other server will back off and try again in a bit. How many and for how long it will try again is determined by the sending server. Some of them are not very patience, and it will report undelivered after only a few attempts. So you would have lost that email.

If you had specified a backup MX, this email may not have been lost. Upon first failure to connect to your server, the sender would see if there is any alternative server to send to. So it connects to your backup mx server. This server spools and queues your message and will try at intervals to send the message to you. It too will though eventually give up.

What is the difference? Simple, you (or whoever controls the backup mx ) is in control how long and often to try connecting to your machine. So if you have a reasonable values and your server is not down for weeks, no mail is lost.

How to implement it? First edit the DNS records again, and add a backup mx with a higher value.

# your server details domain.tld IN MX 10 your.mailserver.name.tld # new backup server domain.tld IN MX 20 your.backupserver.name.tld

Now presuming the other backup mx is a postfix server identical to this, or you are backuing up someone else's server; Go into mysql and create this tables:

CREATE TABLE `backups` ( `pkid` smallint(6) NOT NULL auto_increment, `domain` varchar(128) NOT NULL default '', `transport` varchar(128) NOT NULL default ':[]', `enabled` smallint(6) NOT NULL default '1', PRIMARY KEY (`pkid`), UNIQUE KEY `domain` (`domain`) );

Then still on the backup server, edit main.cf and add these:

relay_domains = mysql:/etc/postfix/mysql_backups.cf transport_maps = mysql:/etc/postfix/mysql_transport.cf

You may choose to have this as the last line in the file, as you may use small cron jobs to modify this ip address, if you don't have a permanent static address. It should contain your IP addres, hence if you do not have a very static IP address, that you need to automatic editing if the postfix file.

proxy_interfaces = 1.2.3.4

If someone comes with a better way, then let me know.

Next create this file /etc/postfix/mysql_backups.cf

user=mail password=apassword dbname=maildb table=backups select_field=domain where_field=domain hosts=127.0.0.1 additional_conditions = and enabled = 1

Next create this file /etc/postfix/mysql_transport.cf

user=mail password=apassword dbname=maildb table=backups select_field=transport where_field=domain hosts=127.0.0.1 additional_conditions = and enabled = 1

You noticed I added a transport lookup. This is a field in both the domain and the backup tables. In domains it is used to determine how to deliver the email, ie either virtual (correct) or local (not used in this howto). When backing up servers, your also need to specify in the transport field how to connect to the correct servers.

Say you are backiup for a friends server, mail.friend.com, for the domains of friend1.com and friend2.com. So you should insert this into your backup table.

INSERT INTO backups (domain,transport) VALUES ('friend1.com' , ':[mail.friend.com]' ), ('friend2.com' , ':[mail.friend.com]' );

The :[] tells to connect directly to this server, not doing any more look ups for valid MX servers.

This shouls now work fine. Further tweaking of the queue values, review these and modify as appropiate. Shorter warning times are good for the sender, so that they realise the email has not arrived yet, but may also be annoying. Tradeoffs.. Look in the first main.cf configurations for ways to do so.

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Local file backup

Here is rough backup script to backup your configurations and mail folders. You may want to backup the folders seperatly as they can quickly grow to GBs. Adding this to a cronjob automates this process. Be aware that you should stop postfix and courier while backing up the mail folders. And that if they have grown large, that this may take some time.

tar czf mail-config.xxxxx.tgz /etc/postfic /etc/courier /etc/spamassassin /etc/clamav /etc/amavis /etc/mysql/my.cnf tar czf mail-fold.xxxx.tgz /var/spool/mail/virtual mysqldump -u mail -papassword -t maildb > data.sql mysqldump -u mail -papassword -d maildb > schema.sql tar czf mail-data.xxx.tgz schema.sql data.sql tar cf mail.xxxxx.tar mail-*.xxxxx.tgz

You may combine a full backup with a intermediate update of what has changed recently only.

tar --newer-mtime "2005-01-01"
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Sender ID & SPF

Further security features is using Microsoft's Sender ID or Pobox's SPF. I'd use SPF as there is much argument over Sender ID.

spf.pobox.com

www.microsoft.com/mscorp/safety/technologies/senderid/

SPF should limit who can send mail on behalf of your domains, and is an open design. I do recommend SPF, with some reservations, detailed below.

While Microsoft is not always entirely evil, as sometimes they do nice things and make some useful software, I would prefer not to be locked into their Sender ID technology.

SPF configuration

The pobox site has some nice SPF generation tools to setup your SPF configuration. Probably best to use theirs.

But the way I have my setup, is generally one domain with detailed SPF, then all other domains just with an SPF alias to it. e.g:

Main domain DNS TXT field:

"v=spf1 a mx a:myserver.example.com include:aspmx.googlemail.com include:gmail.com ~all"

The important elements are:

Then for most of the other domains I would use this DNS TXT field:

"v=spf1 a mx include:example.com ~all"

The important elements are:

And for all these I use ~all!

Ps. Some domains I have added an even stricter SPF, as these are domains that will never send an email.

SPF problem

It is worth noting about SPF, that you should leave the decision to whether to reject or allow the email to the mail servers. Therefor using -all instead of ~all is not a good choice. Leave it to the SPAM scoring by the receiving server, like SpamAssasin does it. You then minimise the risk of false positives.

One of the reason I do discourage -all use, is that SPF has a distinct problem:
It does not like email forwarding or use of backup MX!

Consider this: Your address of lulu@hoopa.com sends a joke email to a few friends. One of these is trixie@bellbell.org.
Trixie's email address is actually an alias and forwards the email to her private webmail account on hotmailnot.com.

Now if your domain, hoopa.com, have a strict SPF set up, which only allows emails to be sent by its mail server. And you/the mail admin has added -all to the SPF, which tells other server to reject emails not from your server. This you think makes sense, spammers can not use your domain for spoof emails.

So what happens: bellbell.org receives the email from lulu, and possible checks the SPF, which is OK, and forwards it on to hotmailnot.com.
However if hotmailnot.com also checks SPF, it will receive the email from bellbell.org, check the SPF to see bellbell.org's mail server is allowed to send emails on behalf hoopa.com. SPF will say No!, and with the -all, hotmailnot.com email server will reject the email!

2nd scenario if lulu email trixie directly at hotmailnot.com, but hotmailnot.com main mail server was down, and email was sent to the backup mx server. When the main server came online again, and the backup spooled the email back to it, the SPF would again fail as the hoopa.com's SPF would not mention hotmailnot.com backup mx as an allowed mail server.

Solution:
Of course you can not list all possible forwarding / backup mx email server that your domain's users might at some point email!
I simple just use the ~all option. Which simple say it is not the expected server, but probably ok.
And if this is added to a scoring by the receiver, then the accumulated spam score might be enough to reject dodgy emails.

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Spam reporting

todo

Reporting spam to Pyzor, Razor and SpamCop, for collaboration in spam fighting.

More detail on SpamCop is here.

pyzor.sourceforge.net

razor.sourceforge.net

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White/Black Lists

todo

You can implement white and black lists to explicitly allow or block domains and users.

You have already visited the option of a blackhole list of known open relays in the postfix configuration.

You can implement further lists inside Postfix or SpamAssassin. Amavisd-new already has a few well known white/black listed items in its config files. SpamAssissin also as a feture to automaticly learn white lists.

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PGP & S/MIME

Adding support for GnuPG and S/MIME increases indiviual security.

This is not implemented on the postfix server side, as this totally a client side option.

However SquirrelMail has a GnuPG option. It is a plugin that can be downloaded from their website. Which can then be enabled via SquirrelMail's config script.

Here is how to create a GnuPG key pair.

# check you have not already got a key gpg --list-keys # then create one gpg --gen-key

To import GnuPG into Evolution; in your settings/preferences edit your account settings and add you private key under the security tab. The private key is found via listing the GnuPG keys as above, then it is the 8 characters after the "sub 1024g/" bit of you key.

To use GnuPG with Thunderbird you need to install EnigMail.

S/MIME is another way to encrypt and/or sign messages. You can create you own certificate or use known organizations like Thawte. (Thawte was originally set up by the Ubuntu founder)

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Relocation notice

If people change addresses, a bounced message stating so if people send email to the old address is quite useful. To implement this in postfix, frst create a lookup table in the database.

CREATE TABLE `relocated` ( `pkid` smallint(6) NOT NULL auto_increment, `oldadr` varchar(128) NOT NULL default '', `newadr` varchar(128) NOT NULL default '', `enabled` tinyint(1) NOT NULL default '1', PRIMARY KEY (`pkid`), UNIQUE KEY `oldadr` (`oldadr`) ) ;

Then add this to /etc/postfix/main.cf

relocated_maps = mysql:/etc/postfix/mysql_relocated.cf

The create this file /etc/postfix/mysql_relocated.cf

user=mail password=apassword dbname=maildb table=relocated select_field=newadr where_field=oldadr hosts=127.0.0.1

Then if pete@domain1.com has changed address to pete.jones@another.org:

INSERT INTO relocated (oldadr,newadr)VALUES ('pete@domain1.com','pete.jones@another.org');

If anyone sends an email to pete@domain.com, they will get a message back stating he has changed address to pete.jones@another.org.

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Pop-before-SMTP

If SASL didn't work, or you are using clients which dont support it, the Pop-Before-SMTP is an easy way around that issue, so that people externally can still securly send mail via your server.

Refer to my 2nd edition on Pop-before-SMTP setup.

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Admin software

todo

Trying out a few admin software might make you life easier, if phpMyAdmin gets to crude. Quick search

More to come later.

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Auto Reply

todo

Postfix have now features to auto reply to an email, while still delivering it to its alias.

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Block Addresses

If you use catch alls, which are useful for some domains, then eventually some addresses will be target for spam. You can then either stop the catch all, or stop indivdual addresses.

By implementing a lookup and adding this restriction to smtpd_recipient_restrictions accomplises this.

check_recipient_access mysql:/etc/postfix/mysql_block_recip.cf, smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, \ check_recipient_access mysql:/etc/postfix/mysql_block_recip.cf, \ reject_non_fqdn_recipient, reject_unauth_destination, \ check_relay_domains

Beware of the order is important here, if any options says ok before check_recipient_access it will ignore it.

Next create mysql_block_recip.cf to lookup addresses. Either create a another table, or add a blocked field to aliases table.

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Throttle Output

todo

For some users with restrictions on bandwidth, you may wish to control how much mail is sendt out. Postfix has long refused to implement these features, out of ideolocial beliefs that mail servers should not be restricted. However there are some ways around this. More to come later.

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Mail Lists

Rich Brown has written a howto on adding Mailman, a mail list program, to my howto. Click here to read it.

Do note it is not part of my howto, so do not contact me regarding it. And although I think it is fine, I can't guarantee it will work.

If you do need assistance or need to talk about it, contact Rich via his howto or use the forums for this howto.

If you want a simple mailling list, it can be implemented by simply seperating aliases in the destination field in the aliases table with a comma.

INSERT INTO aliases (mail,destination) VALUES ( 'listof@domain.com' , 'john@ppp.com,vic@domain.com,jj@somewhere.tld' );
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Google Apps / GMail

Currently writting this one...

I have for various reasons integrated some Google Apps hosted domains into my mail server. And you can still have good control over the addresses by using your server with Google Apps.

More information on Google Apps.

Why

How

Options

The easiest and simples solution is not to have a domain MXed to your server, and simply alias email to those domains. eg All email to joeblogs.co.uk hosted on your server are forwarded to joeblogs.com hosted with google.

You may set up your own server to simple be a mail server backup (mx) for a domain hosted with google. If you are the first priority in the MX details of the DNS, you still have some control, but not all will obey the priority listing. E.g. spammers, but some valid senders as well.

However the one I use and the option where you are most in control is to keep you server as the only MX server in the DNS. And only forward certain aliases onto Google after all your servers checks. Other aliases and user can just use your mail server if you prefer. I will explain how to do this in the next steps.

DNS

You only put your mail server as the mx for the domain in question. Google will complain about this, as it will not be able to verify that email is setup correctly. Ignore this as it will still accept emails.

MySQL tables

You setup you aliases as normal. However you domain table needs tweaking. This is because otherwise your server will just forward the email to itself. You can actually specify aliases in the domain table.

Example: Your domain is bloggs.com. Joe wants to use gmail. Mary does not. to be done to be done

Issues

There are some items you should consider when integrating Google Apps.

Privacy
First there is the privacy issue. This is the same as if you were using Google Apps only or GMail. Google can and will read your email. However probably not a person, but they will use it for commercial reasons, E.g. showing relevant ads. Some people really hate this part and refuse to use Google's mail products. However I trust them a little bit, and do use it.

Spam
If you forward spam, then consider your own servers reputation. Should be okay though.

SPF
If you use SPF for your domain, consider that both your server and google will receive and send mail on behalf of that domin.

Google internally
Be aware Google think they host you domain. So if others inside google, or using google hosted apps or GMail, if they email you, the email may not go via your email server, but directly to the Google Apps for your domain. That could be an issue if not all aliases you have use Google Apps. This needs to be tested more though. Especially as it may only be an issue if Google's servers are part of you domains MXs.

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Maildrop, spam folder and vacation messaging

Villu have documented swapping in Maildrop for virtual transport and automatically deliverin spam to a spam folder. (And links to a post about vacation messaging)

Please read his post here.

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Suggestions?

If you have any suggestions to other ways of extending a postfix server, then fire off a mail to me via the contact form further down.
(Or rather, Id prefer that you write down the extension, and let me know the link! :))

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Elastic Computing Cloud

Impressions

Easy to use. Anyone can use, not just big companies. Very useful. Tools are command line but simple. Firefox extensions work well. Recommended.

I find it very usefull. Basically it is a colo hosting environment. Some may use it as for Saas, ie single scalable application in the cloud, but I use it as a hosting environment for complete servers.

How I plan to use it with my mail servers

Different images to launch for different needs. Good way to scale backup MXs if needed. Can script backup to S3 of mail dirs etc.

Using EC2 with this howto

If you plan to use EC2 to follow this howto, then familiarise yourself with EC2 first. Check the links further down.

Once competent enough on EC2, launch the latest official Ubuntu ec2 image or one of Eric Hammond images. You can cheat by using my other images, but you should really know how the whole server was built by starting from the bottom.

When using EC2 images, be aware of security groups as they restricts access to your server on top of the firewall. Initially you will need SSH (22) access, quite soon you will need SMTP and IMAP ports opened, 25,143,465,587 and 993, and eventually webserver ports of 80 and 443. Read here for tips on securing AMIs.

Also do not terminate your instances without backing up your machine. This you can do by either create your own image. Or backup certain data if you got an image to instantiate from. Back up to S3 or your local machine. Create images only now and then. Backup configurations, database, maildirs more regularily.

Note: You probably want to remove my ssh key from root or ubuntu user's authorized_keys2 file. This should not be present, but may be so please check?

2nd Note: Spamhaus.org lists amazons ec2 ip ranges as dynamic, thus many mail servers will reject emails from it. (Including other people using this howto.) But Spamhaus has a simple web page to remove ips, which they link to in rejection messages. Simple look in your logs, click on the link on follow the instrucions: basically fill in your ip, email and state its for a mail server. Then Spamhaus will remove your IP from their database.

3rd Note: This fix needs to applied to the instances buildt on an early 8.04 base. This is not a problem with the later Hammond or any Canonical based images.

Amazon EC2 Images: AMIs

Public AMIs to use as base:

AMI Description S3 Name Extended from

ami-5059be39

Canonical's Official Ubuntu 8.10 Intrepid 32bit US

canonical-cloud-us/ubuntu-intrepid-20090422-i386

ami-4132d428

Clean with all packages installed but no configuration

flurdy-amis/ubuntu-mail-server-clean-20090529-2

ami-5059be39 (Canonical Official ec2)

ami-0f41a466

Clean with all packages installed but no configuration

flurdy-amis/ubuntu-mail-server-clean-080502-1

ami-ce44a1a7 (Eric Hammond's base)

ami-eb39df82

Just mysql, postfix and courier configured

flurdy-amis/ubuntu-mail-server-basic-20090604-1

ami-4132d428 (Canonical-Clean)

ami-8541a4ec

Just mysql, postfix and courier configured

flurdy-amis/ubuntu-mail-server-simple-080504-1

ami-0f41a466 (Hammond-Clean)

ami-9941a4f0

Including anti spam and anti virus

flurdy-amis/ubuntu-mail-server-spam-080504-1

ami-8541a4ec (Simple)

ami-395fba50

Including TLS and SASL encryption and authentication

flurdy-amis/ubuntu-mail-server-secure-080527-2

ami-9941a4f0 (Spam)

ami-275fba4e

With webmail and admin enabled

flurdy-amis/ubuntu-mail-server-webmail-080527-1

ami-395fba50 (Secure)

ami-xxx

With back up mx

flurdy-amis/ubuntu-mail-server-backup-xxx

ami-275fba4e (Webmail)

ami-xxx

With back up mx only

flurdy-amis/ubuntu-mail-server-backup-only-xxx

ami-395fba50 (Secure)

If you have a comment or question about the ec2 images, please discuss it in the forums?
If you notice a security problem, or I have not cleaned the images properly please let me know?

EC2 Links

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Appendix

No fix computer

About author

Ivar Abrahamsen, an IT Senior Consultant from Norway. Specialising in developing and integrating middleware application systems. Mainly open source and Java based technology stack. Recently moved back to Oslo, Norway after 15 years in Manchester.

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Contact

Remember I have stood on the shoulders of giants. I just ended up with a system that worked for me, and decided to document its evolution.

Before contacting, have you?:

Forums

Use the Ubuntu forums! :)

Please participate in the forums.
If you see an issue you also have, contribute with more information.
And even better if it something you may know how to solve, please let people know.
And especially, if you post a problem, then solve it, let people know what the solution was! (and not just that you solved it...)

I am rubbish in replying to emails, and the forums are read and answered by people whom know a lot more about Postfix than me.

Questions sent to me directly may not be answered for a while or at all unfortunetly.

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Consultancy and advice

Not to be rude, but to try and reduce the volume of emails I get please consider the following:

If you still want my advice or hire me:

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I read your email

Why

Why your own mail server

Main reason: Because you can.
Other good reasons: Basically it leaves you in complete control, to expand, customize and tweak your mail server to your needs. You are not dependant on 3rd party providers, limited by their technology contraints or your budgets. With your own mail server you can add as many aliases, users and domain as you'd like, be as restrictive or open about security, virus, spam, file sizes etc as you prefer. And is it is well known, frequently updated, open source application stack, you can also trust the software you use.

Why I wrote this howto

When I set up my first email server I used a mix of other howtos on the net. And they were so helpfull that I though I would contribute back with my experience. And it has been useful as a recipe script for myself every time I need to install/update a server.

A less angelic reason is that back in 2003 I was setting up mail server for a few friends and collegues. Soon I was getting more request, and being a lazy programmer, I thought.. "Why don't I write a howto and let them do it themselves..." Soon it was listed on postfix.org and I was getting thousends of hits and lots of emails. (blessing in disguise)

Why I wrote this edition

Or rather why no new edition or updates for two years? Well basically no time or need to do so, so basically lazyness...
My last edition was written two years ago, and was pretty complete and thorough so my inclination to write a new one has been low, especially as my own mail server had not changed since then either.

But then my server started crashing so I upgraded it to Ubuntu 8.04 which went pretty smooth, but with a few tweaks. So time for another edition.

This time I expanded reliability to include the possibility of running backup mx servers using Amazon's Elastic Computing Cloud. Note, however this is an optional extra at the end.

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References

New references

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Software Links

Please refer to the previous edition for a list of urls and suiteable downloads. However most are unneccessary with decent package manager.

Difference between Ubuntu versions

I used to distinguish differences, which were avaialble in a previous edition.

Download

Please refer to the previous edition for a complete lists of downloads that are available.

Change log

Brief list of latest changes.

Used to refer to all changes, but got too long. A previous edition contains such a list.

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Todo

Please refer to the previous edition for some old todos....

FAQ

There is not yet an extensive FAQ.

But please, most of the frequent questions have been asked and answered in the forums.
Most are also unneccessary as following the test section will have solved them.

Some question that frequently get sent to me, which first of all should have been asked in the forums and has been answered there many times, which then I tend to ignore are:

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Creative Commons License

This work is licensed under a Creative Commons Attribution-ShareAlike 2.5 License.

flurdy