Introduction to Exim
The Exim package contains a Mail Transport Agent written by the University of Cambridge, released under the GNU Public License.
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
Exim Dependencies
Required
libnsl-2.0.1, File-FcntlLock-0.22 and pcre2-10.42
Optional
TDB (alternative to GDBM, built in LFS), Cyrus SASL-2.1.28, libidn-1.42, Linux-PAM-1.6.0, MariaDB-10.11.6 or MySQL, OpenLDAP-2.6.6, GnuTLS-3.8.3, PostgreSQL-16.1, SQLite-3.45.0, a graphical environment, Heimdal GSSAPI, libspf2, and OpenDMARC
Installation of Exim
Before building Exim, as the root
user you should create the group and user exim
which will run the exim daemon:
groupadd -g 31 exim &&
useradd -d /dev/null -c "Exim Daemon" -g exim -s /bin/false -u 31 exim
Configure Exim with the following commands:
sed -e 's,^BIN_DIR.*$,BIN_DIRECTORY=/usr/sbin,' \
-e 's,^CONF.*$,CONFIGURE_FILE=/etc/exim.conf,' \
-e 's,^EXIM_USER.*$,EXIM_USER=exim,' \
-e '/# USE_OPENSSL/s,^#,,' src/EDITME > Local/Makefile &&
printf "USE_GDBM = yes\nDBMLIB = -lgdbm\n" >> Local/Makefile
If you want to add Linux PAM support, also run the following commands:
sed -i '/# SUPPORT_PAM=yes/s,^#,,' Local/Makefile
echo "EXTRALIBS=-lpam" >> Local/Makefile
Build Exim with the following command:
make
This package does not come with a test suite.
Now, as the root
user:
make install &&
install -v -m644 doc/exim.8 /usr/share/man/man8 &&
install -vdm 755 /usr/share/doc/exim-4.97.1 &&
cp -Rv doc/* /usr/share/doc/exim-4.97.1 &&
ln -sfv exim /usr/sbin/sendmail &&
install -v -d -m750 -o exim -g exim /var/spool/exim
Command Explanations
sed -e ... > Local/Makefile: Most of Exim's configuration options are defined in Local/Makefile
, which is created from the src/EDITME
file. This command specifies the minimum set of options. Descriptions for the options are listed below.
printf ... > Local/Makefile: Setting those variables allows to use GDBM instead of the default Berkeley DB. Remove this command if you have installed Berkeley DB (deprecated).
BIN_DIRECTORY=/usr/sbin
: This installs all of Exim's binaries and scripts in /usr/sbin
.
CONFIGURE_FILE=/etc/exim.conf
: This installs Exim's main configuration file in /etc
.
EXIM_USER=exim
: This tells Exim that after the daemon no longer needs root
privileges, the process needs to hand off the daemon to the exim
user.
USE_OPENSSL
: uncommenting USE_OPENSSL=yes
and USE_OPNSSL_PC=yes
tells the build system to use OpenSSL, and to find the needed libraries with pkg-config.
Uncomment EXIM_MONITOR
: This allows building the Exim monitor program, which requires X Window System support, and is commented out by default.
ln -sfv exim /usr/sbin/sendmail: Creates a link to sendmail for applications which need it. Exim will accept most Sendmail command-line options.
install -v -m750 -o exim -g exim /var/spool/exim: Since /var/spool is owned by root and this version of exim drops root
privileges early, to run as user exim
, it cannot create the /var/spool/exim
directory. As a work around, it is created manually.
Adding Additional Functionality
To utilize some or all of the dependency packages, you'll need to modify Local/Makefile
to include the appropriate directives and parameters to link additional libraries before you build Exim. Local/Makefile
is heavily commented with instructions on how to do this. Listed below is additional information to help you link these dependency packages or add additional functionality.
If you wish to build and install the .info
documentation, refer to https://exim.org/exim-html-4.97.1/doc/html/spec_html/ch04.html#SECTinsinfdoc.
If you wish to build in Exim's interfaces for calling virus and spam scanning software directly from access control lists, uncomment the WITH_CONTENT_SCAN=yes
parameter and review the information found at https://exim.org/exim-html-4.97.1/doc/html/spec_html/ch45.html.
To use a backend database other than GDBM , see the instructions at https://exim.org/exim-html-4.97.1/doc/html/spec_html/ch04.html#SECTdb.
For SSL functionality, see the instructions at https://exim.org/exim-html-4.97.1/doc/html/spec_html/ch04.html#SECTinctlsssl and https://exim.org/exim-html-4.97.1/doc/html/spec_html/ch42.html.
For tcpwrappers functionality, see the instructions at https://exim.org/exim-html-4.97.1/doc/html/spec_html/ch04.html#SECID27.
For information about adding authentication mechanisms to the build, see chapters 33—41 of https://exim.org/exim-html-4.97.1/doc/html/spec_html/index.html.
For information about linking Linux-PAM, refer to the instructions https://exim.org/exim-html-4.97.1/doc/html/spec_html/ch11.html#SECTexpcond.
For information about linking database engine libraries used for Exim name lookups, see the instructions at https://exim.org/exim-html-4.97.1/doc/html/spec_html/ch09.html.
If you wish to add Readline support to Exim when invoked in “test expansion” (-be
) mode, see the information in the -be
section of https://exim.org/exim-html-4.97.1/doc/html/spec_html/ch05.html#id2525974.
You may wish to modify the default configuration and send log files to syslog instead of the default /var/spool/exim/log
directory. See the information at https://exim.org/exim-html-4.97.1/doc/html/spec_html/ch-log_files.html.
A wealth of information can be also found at the Exim Wiki.
Configuring Exim
Config Files
/etc/exim.conf
and /etc/aliases
Configuration Information
Review the file /etc/exim.conf
, and modify any settings to suit your needs. Note that the default configuration assumes that the /var/mail
directory is world writable, but has the sticky bit set. If you want to use the default configuration, issue as the root
user:
chmod -v a+wt /var/mail
A default (nothing but comments) /etc/aliases
file is installed during the package installation if this file did not exist on your system. Create the necessary aliases and start the Exim daemon using the following commands:
cat >> /etc/aliases << "EOF"
postmaster: root
MAILER-DAEMON: root
EOF
/usr/sbin/exim -bd -q15m
Note
To protect an existing /etc/aliases
file, the command above appends these aliases to it. This file should be checked and duplicate aliases removed, if present.
The /usr/sbin/exim -bd -q15m command starts the Exim daemon with a 15 minute interval in processing the mail queue. Adjust this parameter to suit your desires.
Linux PAM Configuration
If you have built Exim with Linux PAM support, you need to create a PAM configuration file to get it working correctly with BLFS.
Issue the following command as the root
user to create the configuration file for Linux PAM:
cat > /etc/pam.d/exim << "EOF"
# Begin /etc/pam.d/exim
auth include system-auth
account include system-account
session include system-session
# End /etc/pam.d/exim
EOF
Boot Script
To automatically start exim at boot, install the /etc/rc.d/init.d/exim
init script included in the blfs-bootscripts-20231119 package:
make install-exim
The bootscript also starts the Exim daemon and dispatches a queue runner process every 15 minutes. Modify the -q<time interval>
parameter in /etc/rc.d/init.d/exim
, if necessary for your installation.
Contents
Installed Programs: exicyclog, exigrep, exim, exim-4.97.1-2, exim_checkaccess, exim_dbmbuild, exim_dumpdb, exim_fixdb, exim_lock, exim_tidydb, eximstats, exinext, exipick, exiqgrep, exiqsumm, exiwhat, and optionally, eximon, eximon.bin, and sendmail (symlink)
Installed Libraries: None
Installed Directories: /usr/share/doc/exim-4.97.1 and /var/spool/exim
Short Descriptions
exicyclog
|
cycles Exim log files
|
exigrep
|
searches Exim log files
|
exim
|
is a symlink to the exim-4.97.1-2 MTA daemon
|
exim-4.97.1-2
|
is the Exim mail transport agent daemon
|
exim_checkaccess
|
states whether a given recipient address from a given host is acceptable or not
|
exim_dbmbuild
|
creates and rebuilds Exim databases
|
exim_dumpdb
|
writes the contents of Exim databases to the standard output
|
exim_fixdb
|
modifies data in Exim databases
|
exim_lock
|
locks a mailbox file
|
exim_tidydb
|
removes old records from Exim databases
|
eximstats
|
generates mail statistics from Exim log files
|
exinext
|
queries remote host retry times
|
exipick
|
selects messages based on various criteria
|
exiqgrep
|
is a utility for selective queue listing
|
exiqsumm
|
produces a summary of the messages in the mail queue
|
exiwhat
|
queries running Exim processes
|
eximon
|
is a start-up shell script for eximon.bin used to set the required environment variables before running the program
|
eximon.bin
|
is a monitor program which displays current information in an X window, and also contains a menu interface to Exim's command line administration options
|