All Linux distributions that I know of come with an MTA of some sort. The most popular is Sendmail. Other popular MTAs include Exim, postfix, and Qmail. This article discusses how to build an advanced mail server which sports all of the latest mail protocols, checks all incoming mail for spam, and scans all incoming and outgoing mail for viruses.
We will use the able Qmail MTA for SMTP and POP3. We will use
vpopmail for virtual domains and
Courier IMAP for
our IMAP server. As our backend we will be using the trusty MySQL RDBMS to
store all of our user information. Since this is a three part series, we will
cover Squirrel Mail in the second part and SpamAssassin, procmail,
QmailScanner, and ClamAV in the third part.
You are assumed to have a working knowledge of Linux, though the steps outlined should work on most UNIX variants with little effort. It is also assumed that you understand how email, in general, works. Finally, it is assumed that you have root access to the machine you wish to turn into an advanced mail server. Debian users are in luck; since this is the distribution I personally run I will include Debian-specific shortcuts whenever possible. If you're using another distribution, you may have to modify the provided installation notes slightly.
All of the distributions that I have worked with either supplied MySQL binaries on the CD or made them available somewhere on the web. For detailed instructions on how to set up MySQL please read MySQL's Installation instructions.
Note: Debian users can
apt-get the packages
Log into your MySQL server as root and type the following commands to create
the database for
mysql> CREATE DATBASE vpopmail; mysql> GRANT ALL ON vpopmail.* -> TO vpopmail@localhost IDENTIFIED BY 'password';
You can change the names of the database, user, and password, but make sure
to keep track of them for later use. You also may wish to change the security
preferences for your
vpopmail user, but before you do read up on
the MySQL GRANT statement.
This step is optional. If you wish to run your webmail via a secure connection or enable IMAP-SSL or POP3-SSL, you will need to install OpenSSL. Your distribution should come with OpenSSL packages. Be sure to install the development versions of those packages so that we can compile Courier and Qmail from source.
Note: Debian users can
apt-get the package
Qmail was written by D. J. Bernstein (DJB) as a replacement for Sendmail. Qmail differs greatly from Sendmail so before you jump headlong into installing Qmail, you should download the source and read through the documentation. Furthermore, it may be in your best interest to read Life with qmail by Dave Sill.
ucspi-tcp is a simple TCP Server/Client created by DJB for "building TCP client-server applications" and is required to run Qmail. After you have downloaded and extracted the source, change into the directory and compile the code.
bash$ make bash$ make setup check
You can read over DJB's installation instructions on his How to install
ucspi-tcp page. Also, be sure to turn off any affected ports
/etc/inetd.conf and restart your
Note: Debian users can
apt-get the package
daemontools "is a collection
of tools for managing UNIX services." This is the preferred way to run Qmail,
but is not required to run Qmail. To install it, first make the
/package directory it expects.
bash$ mkdir -p /package bash$ chmod 1755 /package bash$ cd /package
Download the daemontools package into the
and untar it. Next, run the installer:
bash$ cd admin/daemontools-0.76 bash$ package/install
You can read over DJB's installation instructions on his How to install daemontools page.
Note: Debian users can
daemontools-installer. Debian users may also wish to check out
qmail-sv as well.
Version 1.03 is the latest version of Qmail. The default installation of Qmail is very vanilla and will require some minor patching to do what we wish to do. Particularily we will want to install:
Bill Guenter's famous Qmail QUEUE patch, which will allow us to run alternate programs as Qmail's queue.
Bill Shupp's maildir++ patch, which will fix
vpopmail and Qmail quota issues.
Eric M. Johnston's SMTP-AUTH patch, which allows users outside of your network to send email after they have authenticated.
The installation process for Qmail is very hands on and requires you to be
familiar with the command prompt. Before installing, please read
INSTALL.alias. You may wish to look over the other
INSTALL.* files as well.
bash$ mkdir /var/qmail bash$ groupadd nofiles bash$ useradd -g nofiles -d /var/qmail/alias alias bash$ useradd -g nofiles -d /var/qmail qmaild bash$ useradd -g nofiles -d /var/qmail qmaill bash$ useradd -g nofiles -d /var/qmail qmailp bash$ groupadd qmail bash$ useradd -g qmail -d /var/qmail qmailq bash$ useradd -g qmail -d /var/qmail qmailr bash$ useradd -g qmail -d /var/qmail qmails bash$ make setup check bash$ ./config-fast example.com bash$ (cd ~alias; touch .qmail-postmaster .qmail-mailer-daemon .qmail-root) bash$ chmod 644 ~alias/.qmail*
Make sure to change
example.com to the actual hostname of your
Note: Debian users can
qmail-src, however, the package does not include the SMTP-AUTH or maildir++ patches. Alternatively, you could try Garrit Pape's Debian packages.
Once you have Qmail installed, make sure it starts up during your boot sequence. There are a several init scripts available on the web, one of which can be found here. The script says it is for Red Hat, but it should work for any distro with a little modification.
bash$ cp qmailctl.txt /etc/init.d/qmail
Before you start Qmail, you need to set up
scripts which control how Qmail responds to various requests.
bash$ mkdir -p /var/qmail/supervise/qmail-send/log bash$ mkdir -p /var/qmail/supervise/qmail-smtpd/log bash$ mkdir -p /var/qmail/supervise/qmail-pop3d/log
After you are done setting up the directories you will need to create all of the controlling scripts.
#!/bin/sh exec env - PATH="/var/qmail/bin:$PATH" qmail-start ./Maildir/
#!/bin/sh exec /usr/local/bin/setuidgid qmaill /usr/local/bin/multilog t \ s10000000 n30 /var/log/qmail/send
#!/bin/sh QMAILDUID=`id -u qmaild` NOFILESGID=`id -g qmaild` exec /usr/local/bin/softlimit -m 2000000 \ /usr/local/bin/tcpserver \ -H -l hostname.yourdomain.com \ -v -x /etc/tcp.smtp.cdb \ -c 20 -R -u "$QMAILDUID" -g "$NOFILESGID" 0 smtp \ /var/qmail/bin/qmail-smtpd hostname.yourdomain.com \ /var/lib/vpopmail/bin/vchkpw /bin/true 2>&1
#!/bin/sh exec /usr/local/bin/setuidgid qmaill /usr/local/bin/multilog t s10000000 \ n30 /var/log/qmail/smtpd
#!/bin/sh exec /usr/local/bin/softlimit -m 3000000 \ /usr/local/bin/tcpserver \ -H -l example.com \ -v -x /etc/tcp.pop3.cdb -c 30 -R 0 pop3 \ /var/qmail/bin/qmail-popup example.com \ /var/lib/vpopmail/bin/vchkpw /var/qmail/bin/qmail-pop3d Maildir 2>&1
#!/bin/sh exec /usr/local/bin/setuidgid qmaill /usr/local/bin/multilog t s10000000 \ n30 /var/log/qmail/pop3d
After you have taken care of all of the scripts, the last steps are to
chmod the scripts, make the log directories and make
daemontools aware of the new service.
bash$ chmod 755 /var/qmail/supervise/qmail-send/run bash$ chmod 755 /var/qmail/supervise/qmail-send/log/run bash$ chmod 755 /var/qmail/supervise/qmail-smtpd/run bash$ chmod 755 /var/qmail/supervise/qmail-smtpd/log/run bash$ chmod 755 /var/qmail/supervise/qmail-pop3d/run bash$ chmod 755 /var/qmail/supervise/qmail-pop3d/log/run bash$ mkdir /var/log/qmail bash$ mkdir /var/log/qmail/smtpd bash$ mkdir /var/log/qmail/send bash$ mkdir /var/log/qmail/pop3d bash$ chown -R qmaill /var/log/qmail bash$ ln -s /var/qmail/supervise/qmail-send /service bash$ ln -s /var/qmail/supervise/qmail-smtpd /service bash$ ln -s /var/qmail/supervise/qmail-pop3d /service bash$ /etc/init.d/qmail start
The wonderful folks over at Inter7 developed
vpopmail to handle the management of virtual domains using Qmail. Unfortunately
vpopmail is limited to a measly 23 million virtual hosts,
of which each are limited to only 23 million users. So if you have
more than 529 trillion users you may need to look elsewhere.
vpopmailUser and Group
As noted in
INSTALL file, "[the]
FreeBSD folks have reserved 89 for the group and 89 for the user for
vpopmail." You will probably want to ensure
is running as uid and gid 89.
bash$ groupadd -g 89 vchkpw bash$ useradd -g vchkpw -u 89 -d /path/to/where/you/want vpopmail
you can put it wherever you wish. Just remember that all email messages will be
/var/lib/vpopmail, so choose a partition with plenty of
The first thing you need to do is set up
vpopmail for MySQL.
This is done by doing some light code editing in a header file. Fire up your
favorite editor. Open up the file
vmysql.h and change the
following lines to match the configuration you set up in the MySQL section of
#define MYSQL_UPDATE_SERVER "localhost" #define MYSQL_UPDATE_USER "vpopmail" #define MYSQL_UPDATE_PASSWD "password" #define MYSQL_READ_SERVER "localhost" #define MYSQL_READ_USER "vpopmail" #define MYSQL_READ_PASSWD "password"
After you have finished editing
vmysql.h, compile the program.
Be sure to run
./configure --help before configuring the software.
Below is what I used to enable MySQL support and install
bash$ ./configure \ --enable-mysql=y --enable-auth-logging=n --enable-mysql-logging=n --enable-logging=e --enable-valias=y --enable-passwd=n --enable-defaultquota=15728640 --enable-roaming-users=y
There are a few things to note in the above configuration that you may want to change to suit your needs.
--enable-auth-logging because SquirrelMail logs in
and out every time a page is loaded, which can make logs grow quickly on active
e option to
--enable-logging enables logging
only of errors.
--enable-defaultquota The default quota can be computed by
using the equation (MB * 1024 * 1024) where MB is the number of megabytes you
would like your default quota to be.
You may need to specify the location of your MySQL include and library
only virtual users will have access to our mail server.
NFS users may wish to look at the
--enable-file-sync options. Because Qmail uses the alternative Maildir format to store messages, it works quite nicely with NFS.
After running the configure script, compile and install
vpopmail with the following commands:
bash$ make bash$ make install-strip
Note: Debian has packages for
vpopmail, however I could not
get them working properly with MySQL.
Adding domains is extremely simple. Before you create a domain you will want
to read the man pages for
vadddomain. There are options for mail
delivery, quotas, etc.
bash$ /path/to/vpopmail/bin/vadddomain example.com password
password is the password for firstname.lastname@example.org, who will
be the administrator for that domain. After you have created the domain your
domain's user directories and
.qmail files will exist in
You can use either
qmailadmin to create users or
bash$ /path/to/vpopmail/bin/vadduser email@example.com password
Courier IMAP is another piece of software by Inter7. It's a simple IMAP
server that was created specifically to work with Maildir. Read over the
INSTALL file before we get started to familiarize yourself with
the installation process.
bash$ ./configure \ --prefix=/usr/local/courier-imap \ --with-ssl \ --with-authvchkpw bash$ make bash$ make install bash$ make install-configure
--with-ssl is optional
Once you are done installing Courier IMAP, you need to edit a few
configuration options in its configuration file. Open
/usr/local/courier-imap/etc/imapd in your favorite editor and
change the following options.
editor's note: some of these options could use further explanation
100. (Many users will
be using the web interface, which all come from a single IP.)
"-nodnslookup -noidentlookup -user=vpopmail -group=vchkpw".
IMAP_EMPTYTRASH=Trash:7,Sent:30 to whatever you want.
This option tells Courier to clear out these folders every 7 and 30 days,
respectively. You can add extra folders there as well that you wish to have
the server empty periodically.
After you have all of this up and running, you should be ready to fire up
your IMAP server. To start Courier IMAP at boot, copy
/usr/local/src/courier-imap-1.7.x/courier-imap.sysvinit to the
directory appropriate for your distro (many use
bash$ cp /usr/local/src/courier-imap-1.7.x/courier-imap.sysvinit \ /etc/init.d/courier-imap bash$ chmod 744 /etc/init.d/courier-imap bash$ /etc/init.d/courier-imap start
qmailadmin is a CGI interface to
vpopmail. It is totally optional, but will make administering your virtual domains, users, forwards, etc. much easier. Not only does it allow your postmaster to create and manage accounts, forwards, and aliases, but it allows users to log in and change passwords, set vacation messages, etc.
qmailadmin requires EZMLM, DJB's mailing list manager, which you may not wish to install. You can skip this step.
autoresponder is a prerequisite of
qmailadmin and does basic auto responding. After you have extracted the source, change into the package's directory.
bash$ make bash$ make man bash$ make setup
EZMLM is DJB's mailing list software which works great with Qmail. EZMLM's main website has been down for quite some time. I suggest you grab the source from DJB's EZMLM page. You will most likely wish to patch EZMLM with the famous IDX patch which adds a plethora of options. I found a working mirror where you can download ezmlm-idx-0.40.tar.gz. After you have extracted both the EZMLM source and the IDX patch, install EZMLM.
bash$ mv ezmlm-idx-0.xx/* ezmlm-0.53/ bash$ cd ezmlm-0.53 bash$ patch < idx.patch bash$ make mysql bash$ make clean bash$ make && make man bash$ make setup
bash$ ./configure \ --enable-cgibindir=/path/to/your/cgi-bin --with-htmllibdir=/path/to/your/html/docroot --enable-imagedir=/path/to/your/images/directory
There are several options to look into if you plan to allow clients to
administer their own domains.
--enable-maxmailinglists are just two of the options you may wish
to use. Be sure to check out
./configure --help for a complete
list of options.
bash$ make bash$ make install-strip
After you have installed
qmailadmin, you should be able to log
in to to
http://example.com/cgi-bin/qmailadmin to administer your
Now that you have everything installed and have created your users, you
should be able to log in. Because
vpopmail uses virtual hosts your
username will be
firstname.lastname@example.org, which is important to
remember. Because of Qmail's flexibility and the power of
vpopmail's MySQL support you can easily create domains and hand
over the ability to manage accounts to your customers, which leaves plenty of
Now that your mail server is running the hard part is over, but it is not yet complete. The second part of our series will cover installing Apache+PHP and Squirrel Mail. We will also customize Squirrel Mail with a few plugins that will make managing your web mail system a lot easier. In the third and final part of our series, you will see how easy it is to integrate both virus and spam protection into your new mail server.
Joe Stump is the Lead Architect for Digg where he spends his time partitioning data, creating internal services, and ensuring the code frameworks are in working order.
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