Complete Virtual Mail Server/System Setup and Packages

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This article is part of the Complete Virtual Mail Server series.

System deployment

Web Server

First, a web server needs to be chosen. This web server will handle the roundcube and postfixadmin web interfaces. Since the database will be generated using postfixadmin, a web server needs to be installed. After the initial setup, however, the web server may be uninstalled again.

There are a few popular choices for a web server:

Install the web server by following the information on the Gentoo Wiki.

Any of them work equally well, however some parts of the guide specifically reference Apache. For those without prior experience it is thus recommended to choose Apache, while the more knowledgeable user is given no recommendation.

Imap service

Here, too, a choice needs to be made. The popular options include:

Dovecot is a reliable, secure and incredibly fast imap service supporting most known storage formats. It offers high configurability while still keeping the setup process manageable for beginners due to sane defaults. Offering many modern features, it reputes itself as one of the only standarts-compliant mail servers.[1]

Courier is a solid, stable imap service. While not as fast as Dovecot, it instead claims higher reliability and has a longer track record. It is rather easy to set up, though it lacks quite a few features expected from modern imap services, like easy configuration of namespaces. Still, it is a reputable and highly reliable choice.

Cyrus is an imap service well known for it's sheer number of options and incredibly high configurability. It is not supported in this guide as of yet, but contributions are always welcome.

Install the chosen package with:

root #emerge --ask dovecot


root #emerge --ask courier-authlib courier-imap

If the courier-imap route is chosen, cyrus-sasl should also be installed:

root #emerge --ask cyrus-sasl
Dovecot is recommended for most users, as it's modern features, security and reliable performance are strong arguments in its favor. Courier-imap remains a viable choice for many users, but it's lack of some modern features prevent it from being recommended.

Database backend

Choose between dev-db/postgresql and dev-db/mysql. To select either one of them, set the mysql or the postgres USE flags in /etc/portage/make.conf.

Both are well-known and reputable options, but some parts of this guide (especially with regards to dovecot) do not have relevant MySQL sections yet. Thus Postgresql is the recommended database backend.

Web apps

In order to configure the web server as recommended by this guide, both www-apps/postfixadmin and mail-client/roundcube should be installed.

Postfixadmin is strictly required due to being used to set up the database backend. Roundcube is not strictly required, though a necessary part for any webmail functionality. Installation should be done once the appropriate part of the guide is reached.

Further packages

Postfix is a necessary component of this setup, thus it needs to be installed. For instructions, please read the bottom of this page.

In order to support spam and virus filtering, mail-filter/amavisd-new, mail-filter/spamassassin and app-antivirus/clamav need to be installed. Appropriate instructions are to be found here: Anti-Spam measures.


At this point most users just want to get to the good stuff. Before digging into this, the following is strongly suggested to read through:

  1. READ THIS DOCUMENT. This is a long document and there are many opportunities to go off the rails. Take the time to become familiar with all of the steps and understand the role that each of the packages play, and recovery from mistakes will be much quicker.
  2. Not all of the packages included in this HOWTO are required to get the basic mail server working. SMTP Authorization, Web Administration Tools, SPAM filtering, etc. are not absolute necessities to offer mail services, just really good things to have. By reading through this first, figure out which ones are required and which ones aren't to save the work of installing them to begin with.
  3. Like all HOWTOs, this one pretty well assumes that everything in the system is going to be where it should be and that everything will go right at each step. In reality, things will go wrong, at which time the web will prove to be an invaluable resource in resolving whatever issues may occur.
  4. A key to testing all of this is having at least one domain (and two would be better to test virtual domains), with the appropriate MX records setup. There are many DNS options out there so a couple of domains and supporting DNS services shouldn't cost more then $10 for the year. This is not the time to go cheap. Invest the money and make life a whole lot simpler.
  5. Pay close attention to the messages displayed after emerging any packages. Depending on the state of the machine when the installation was started, the installation of these packages may result in the need to update some of the configuration files. Use dispatch-conf to resolve this. There are no instructions in this HOWTO covering this as this is pretty system-specific.
  6. Be sure that system is up to date. Complete an emerge --sync and emerge -uDNva @world before starting this. A number of problems may occur due to old applications not mixing with new utilities.

Finally, to avoid a lot of rework on this, check USE flags variables in the /etc/portage/make.conf file before starting to compiling anything. If the wrong flags are set, it is most likely that things need to be recompiled later to ensure the support needed to make this work is compiled in.

USE flag Description
authdaemond Needed by courier-imap if the courier route is taken.
bzip2 Required by the virus scanner.
clamdtop ClamAV 'top' like tool. If heavy load on the mail server exists, due to clamav running a lot, clamdtop can help a lot debugging it.
crypt Crypt functions for PHP. Used for passwords in the web interface.
geoip IP to Location mapping for spam prevention. This only allows to resolve IPs to their locations, the location of the server will not be disclosed by this.
imap One of the main interfaces offered by this HOWTO to let clients access e-mail.
ipv6 If the system has IPv6 connectivity, enable this. Tested extensively and works well in Postfix, Courier and Apache.
maildir Choose the maildir format supported by Postfix (one of the reasons for choosing Postfix). This is heavily recommended.
mbox Absolutly do not use mbox.
mysql If mysql support is desired enable this.
postgres If postgres support is desired enable this.
sasl Simple Authentication and Security Layer. Strongly recommended.
spamassassin Recommended if spam filtering is required.
spell Spell checking for PHP. Used by webmail.
ssl Secure Socket Layer connections. Absolutely necessary if any security is to be achieved.
urandom Used by cyrus-sasl. Strongly recommended.
vda Quota support for postfix. Adds support for virtual delivery agent quota enforcing. No support in Postfix 3.0, which is now stable in portage.
vhosts Support virtual hosts. Strongly recommended.

With the correct USE flags set, emerging just mail-mta/postfix will pull in most, if not all the right packages.

root #emerge --ask postfix