Beyond Linux® From Scratch (systemd Edition) - Version r12.0-816

Chapter 21. Mail Server Software

Dovecot-2.3.21

Introduction to Dovecot

Dovecot is an Internet Message Access Protocol (IMAP) and Post Office Protocol (POP) server, written primarily with security in mind. Dovecot aims to be lightweight, fast and easy to set up as well as highly configurable and easily extensible with plugins.

[Note]

Note

Development versions of BLFS may not build or run some packages properly if LFS or dependencies have been updated since the most recent stable versions of the books.

Package Information

Additional Downloads

Dovecot Dependencies

Required

libtirpc-1.3.4

Optional

CLucene-2.3.3.4, ICU-74.1, libcap-2.69 with PAM, Linux-PAM-1.5.3, Lua-5.4.6, MariaDB-10.11.5 or MySQL, OpenLDAP-2.6.6, PostgreSQL-16.1, SQLite-3.44.2, Valgrind-3.22.0, xfsprogs-6.5.0, Cassandra, lz4, stemmer and libsodium

Installation of Dovecot

There should be dedicated users and groups for unprivileged Dovecot processes and for processing users' logins. Issue the following commands as the root user: 

groupadd -g 42 dovecot &&
useradd -c "Dovecot unprivileged user" -d /dev/null -u 42 \
        -g dovecot -s /bin/false dovecot &&
groupadd -g 43 dovenull &&
useradd -c "Dovecot login user" -d /dev/null -u 43 \
        -g dovenull -s /bin/false dovenull

First, apply a patch to fix problems with OpenSSL-3: 

patch -Np1 -i ../dovecot-2.3.21-openssl3_fixes-1.patch

Next, apply a patch to fix a security vulnerability: 

patch -Np1 -i ../dovecot-2.3.21-security_fix-1.patch

Install Dovecot by running the following commands: 

CPPFLAGS="-I/usr/include/tirpc" \
LDFLAGS+=" -ltirpc" \
./configure --prefix=/usr                          \
            --sysconfdir=/etc                      \
            --localstatedir=/var                   \
            --docdir=/usr/share/doc/dovecot-2.3.21 \
            --disable-static                       &&
make

To test the results, issue make -k check.

Now, as the root user: 

make install

Command Explanations

CPPFLAGS=... LDFLAGS+=...: build with libtirpc instead of the recently removed RPC code provided by GlibC.

--disable-static: This switch prevents installation of static versions of the libraries.

--with-ldap: This switch enables OpenLDAP authentication support.

--with-pgsql: This switch enables PostgreSQL database support.

--with-mysql: This switch enables MySQL database support.

--with-sqlite: This switch enables SQLite database support.

--with-lucene: This switch enables CLucene full text search support.

--with-lua: This switch enables Lua plugin support. This includes a mail and push notification plugin.

Configuring Dovecot

Config Files

/etc/dovecot/dovecot.conf, /etc/dovecot/conf.d/*, and /etc/dovecot/local.conf

Configuration Information

Copy an example configuration, which you can use as a starting point: 

cp -rv /usr/share/doc/dovecot-2.3.21/example-config/* /etc/dovecot

The following configuration is a simple proof of concept with IMAP service using local users for authentication and mailbox location. Reading files from the conf.d directory is commented out since the included example configuration requires OpenSSL and Linux PAM. 

sed -i '/^\!include / s/^/#/' /etc/dovecot/dovecot.conf &&
chmod -v 1777 /var/mail &&
cat > /etc/dovecot/local.conf << "EOF"
protocols = imap
ssl = no
# The next line is only needed if you have no IPv6 network interfaces
listen = *
mail_location = mbox:~/Mail:INBOX=/var/mail/%u
userdb {
  driver = passwd
}
passdb {
  driver = shadow
}
EOF

You will definitely want to read the official documentation at https://wiki2.dovecot.org/ if you plan to use Dovecot in a production environment.

Systemd Unit

To start the dovecot daemon at boot, enable the previously installed systemd unit with the following command: 

systemctl enable dovecot

Contents

Installed Programs: doveadm, doveconf, dovecot, dovecot-sysreport, and dsync (symbolic link)
Installed Libraries: various internal plugins in /usr/lib/dovecot
Installed Directories: /etc/dovecot, /usr/{include,lib,libexec,share}/dovecot and /usr/share/doc/dovecot-2.3.21

Short Descriptions

doveadm

is the Dovecot administration tool

doveconf

is Dovecot's configuration dumping utility

dovecot

is the IMAP and POP server

dovecot-sysreport

prints system information that is useful to the Dovecot developers when submitting bug reports upstream

dsync

is Dovecot's mailbox synchronization utility