We use Ubuntu 22.04
Step 1: install Exim via command line:
apt install exim4
... Selecting previously unselected package exim4-config. (Reading database ... 73634 files and directories currently installed.) Preparing to unpack .../exim4-config_4.95-4ubuntu2.5_all.deb ... Unpacking exim4-config (4.95-4ubuntu2.5) ... Selecting previously unselected package exim4-base. Preparing to unpack .../exim4-base_4.95-4ubuntu2.5_amd64.deb ... Unpacking exim4-base (4.95-4ubuntu2.5) ... Selecting previously unselected package libgnutls-dane0:amd64. Preparing to unpack .../libgnutls-dane0_3.7.3-4ubuntu1.5_amd64.deb ... Unpacking libgnutls-dane0:amd64 (3.7.3-4ubuntu1.5) ... Selecting previously unselected package exim4-daemon-light. Preparing to unpack .../exim4-daemon-light_4.95-4ubuntu2.5_amd64.deb ... Unpacking exim4-daemon-light (4.95-4ubuntu2.5) ... Selecting previously unselected package exim4. Preparing to unpack .../exim4_4.95-4ubuntu2.5_all.deb ... Unpacking exim4 (4.95-4ubuntu2.5) ... Setting up libgnutls-dane0:amd64 (3.7.3-4ubuntu1.5) ... Setting up exim4-config (4.95-4ubuntu2.5) ... Adding system-user for exim (v4) Setting up exim4-base (4.95-4ubuntu2.5) ... exim: DB upgrade, deleting hints-db Created symlink /etc/systemd/system/timers.target.wants/exim4-base.timer → /lib/systemd/system/exim4-base.timer. exim4-base.service is a disabled or a static unit, not starting it. Setting up exim4-daemon-light (4.95-4ubuntu2.5) ... Setting up exim4 (4.95-4ubuntu2.5) ... Processing triggers for man-db (2.10.2-1) ... Processing triggers for libc-bin (2.35-0ubuntu3.7) ... Scanning processes... Scanning candidates... Scanning processor microcode... Scanning linux images... The processor microcode seems to be up-to-date. Restarting services... systemctl restart irqbalance.service packagekit.service php8.1-fpm.service polkit.service supervisor.service Service restarts being deferred: systemctl restart networkd-dispatcher.service systemctl restart unattended-upgrades.service No containers need to be restarted. No user sessions are running outdated binaries. No VM guests are running outdated hypervisor (qemu) binaries on this host.
After the installation is complete, you can check the installed Exim version with the command:
exim --version
result:
root@tutorialspots ~ # exim --version Exim version 4.95 #2 built 11-Jan-2024 13:16:58 Copyright (c) University of Cambridge, 1995 - 2018 (c) The Exim Maintainers and contributors in ACKNOWLEDGMENTS file, 2007 - 2020 Berkeley DB: Berkeley DB 5.3.28: (September 9, 2013) Support for: crypteq iconv() IPv6 GnuTLS TLS_resume move_frozen_messages DANE DKIM DNSSEC Event I18N OCSP PIPE_CONNECT PRDR Experimental_Queue_Ramp SOCKS SRS TCP_Fast_Open Lookups (built-in): lsearch wildlsearch nwildlsearch iplsearch cdb dbm dbmjz dbmnz dnsdb dsearch nis nis0 passwd Authenticators: cram_md5 external plaintext Routers: accept dnslookup ipliteral manualroute queryprogram redirect Transports: appendfile/maildir/mailstore autoreply lmtp pipe smtp Fixed never_users: 0 Configure owner: 0:0 Size of off_t: 8 Configuration file search path is /etc/exim4/exim4.conf:/var/lib/exim4/config.autogenerated Configuration file is /var/lib/exim4/config.autogenerated
Step 2: Configure Exim
use command:
dpkg-reconfigure exim4-config
Edit file /etc/exim4/conf.d/main/02_exim4-config_options , add line
disable_ipv6 = true
Restart service exim4
Step 3: SPF configuration:
Add SPF Record to DNS :
Log in to your domain’s DNS admin account. Usually through the administration interface of the domain name provider or DNS service you are using.
Add a new TXT record with the following content:
v=spf1 a:mail.yourdomain.com ip4:<server_ip> include:_spf.google.com ~all
example
v=spf1 a:mail.yourdomain.com ip4:11.11.11.11 include:_spf.google.com ~all
Save changes.
read more about SPF: https://support.google.com/a/answer/10685031?sjid=14440567733282704103-AP
Step 4: Install OpenDKIM using the following command:
sudo apt install opendkim opendkim-tools
... Unpacking libopendkim11:amd64 (2.11.0~beta2-6) ... Selecting previously unselected package libmemcached11:amd64. Preparing to unpack .../01-libmemcached11_1.0.18-4.2ubuntu4_amd64.deb ... Unpacking libmemcached11:amd64 (1.0.18-4.2ubuntu4) ... Selecting previously unselected package libmilter1.0.1:amd64. Preparing to unpack .../02-libmilter1.0.1_8.15.2-22ubuntu3_amd64.deb ... Unpacking libmilter1.0.1:amd64 (8.15.2-22ubuntu3) ... Selecting previously unselected package libopendbx1. Preparing to unpack .../03-libopendbx1_1.4.6-16_amd64.deb ... Unpacking libopendbx1 (1.4.6-16) ... Selecting previously unselected package librbl1:amd64. Preparing to unpack .../04-librbl1_2.11.0~beta2-6_amd64.deb ... Unpacking librbl1:amd64 (2.11.0~beta2-6) ... Selecting previously unselected package libunbound8:amd64. Preparing to unpack .../05-libunbound8_1.13.1-1ubuntu5.4_amd64.deb ... Unpacking libunbound8:amd64 (1.13.1-1ubuntu5.4) ... Selecting previously unselected package libvbr2:amd64. Preparing to unpack .../06-libvbr2_2.11.0~beta2-6_amd64.deb ... Unpacking libvbr2:amd64 (2.11.0~beta2-6) ... Selecting previously unselected package dns-root-data. Preparing to unpack .../07-dns-root-data_2023112702~ubuntu0.22.04.1_all.deb ... Unpacking dns-root-data (2023112702~ubuntu0.22.04.1) ... Selecting previously unselected package opendkim. Preparing to unpack .../08-opendkim_2.11.0~beta2-6_amd64.deb ... Unpacking opendkim (2.11.0~beta2-6) ... Selecting previously unselected package libopendbx1-sqlite3. Preparing to unpack .../09-libopendbx1-sqlite3_1.4.6-16_amd64.deb ... Unpacking libopendbx1-sqlite3 (1.4.6-16) ... Selecting previously unselected package opendkim-tools. Preparing to unpack .../10-opendkim-tools_2.11.0~beta2-6_amd64.deb ... Unpacking opendkim-tools (2.11.0~beta2-6) ... Setting up libopendkim11:amd64 (2.11.0~beta2-6) ... Setting up libopendbx1 (1.4.6-16) ... Setting up dns-root-data (2023112702~ubuntu0.22.04.1) ... Setting up libunbound8:amd64 (1.13.1-1ubuntu5.4) ... Setting up libmilter1.0.1:amd64 (8.15.2-22ubuntu3) ... Setting up libmemcached11:amd64 (1.0.18-4.2ubuntu4) ... Setting up librbl1:amd64 (2.11.0~beta2-6) ... Setting up libvbr2:amd64 (2.11.0~beta2-6) ... Setting up libopendbx1-sqlite3 (1.4.6-16) ... Setting up opendkim-tools (2.11.0~beta2-6) ... Setting up opendkim (2.11.0~beta2-6) ... Created symlink /etc/systemd/system/multi-user.target.wants/opendkim.service → /lib/systemd/system/opendkim.service. Processing triggers for man-db (2.10.2-1) ... Processing triggers for libc-bin (2.35-0ubuntu3.7) ... Scanning processes... Scanning processor microcode... Scanning linux images... Running kernel seems to be up-to-date. The processor microcode seems to be up-to-date. No services need to be restarted. No containers need to be restarted. No user sessions are running outdated binaries. No VM guests are running outdated hypervisor (qemu) binaries on this host.
Step 5: Generate a key pair for DKIM with the following command:
sudo opendkim-genkey -t -s <selector> -d <your_domain>
Replace
<selector>
with a name of your choice (eg:postmaster) and
If you want to use email admin@yourdomain.com you use
<selector>
is admin
This command will create two files:
<selector>.private
and
<selector>.txt
Step 6: create OpenDKIM’s key directory: /etc/opendkim/keys/
mkdir -p /etc/opendkim/keys/<your_domain>
Step 7: Move the private key into OpenDKIM’s key directory:
sudo mv <selector>.private /etc/opendkim/keys/<your_domain>/<selector>.private
Step 8: Specify ownership for the lock file
sudo chown opendkim:opendkim /etc/opendkim/keys/<your_domain>/<selector>.private
sudo chown opendkim:opendkim /etc/opendkim/keys/tutorialspots.com/postmaster.private
Step 9: Edit OpenDKIM’s configuration file /etc/opendkim.conf
uncomment then change default:
#Domain example.com #Selector 2020 #KeyFile /etc/dkimkeys/example.private
To:
Domain <your_domain> Selector <selector> KeyFile /etc/opendkim/keys/<your_domain>/<selector>.private
Step 10: edit file /etc/default/opendkim
you will see
# default: SOCKET=local:$RUNDIR/opendkim.sock # listen on all interfaces on port 54321: #SOCKET=inet:54321 # listen on loopback on port 12345: #SOCKET=inet:12345@localhost # listen on 192.0.2.1 on port 12345: #SOCKET=inet:12345@192.0.2.1
change to
# default: #SOCKET=local:$RUNDIR/opendkim.sock # listen on all interfaces on port 54321: #SOCKET=inet:54321 # listen on loopback on port 12345: SOCKET="inet:8891@localhost" # listen on 192.0.2.1 on port 12345: #SOCKET=inet:12345@192.0.2.1
Step 11: Restart the OpenDKIM service
sudo systemctl restart opendkim
Step 12: Add DKIM Records to DNS :
open file
<selector>.txt
Example:
cat postmaster.txt
You will see content like:
postmaster._domainkey IN TXT ( "v=DKIM1; h=sha256; k=rsa; t=y; "
"p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAjz0DntbdxG6wc3BbxidEQMLB3NOUq/0zZe6a8hwLjNuRUNngtk2pFLxKhzXrwud9lfVZdts/tvQ0p/eWpi5VsKeaJf9eE/Vm00doL4lg+U7AWwWw/kSsa8H9k/wlS5LQzKNol33ysjFEtTD/K12KzNPmfGB0R727yaocA4SvKMz2iShzu8uwKiREIR7bLLxXtLKVHlI4zdLEIy"
"kCcy8NZ16mMTZ7qXqmPabXmjY4+aeIhFXf8b87ELPmG7zZwvdyfFg82c7hmNN8MFgTGBLu52QWb3umvAvmZRDrSET+it4sfPH1ikPdRBBCa0l7AUyUmIBzM0XXtVvC1iHCMXL7YQIDAQAB" ) ; ----- DKIM key postmaster for yourdomain.com
you only need to copy parts
p=<public_key>
of the recording.
p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAjz0DntbdxG6wc3BbxidEQMLB3NOUq/0zZe6a8hwLjNuRUNngtk2pFLxKhzXrwud9lfVZdts/tvQ0p/eWpi5VsKeaJf9eE/Vm00doL5lg+U7AWwWw/kSsa8H9k/wlS4LQzKNol33ysjFEtTD/K12KzNPmfGB0R727yaocA4SvKMz2iShzu8uwKiREIR7bLLxXtLKVHlI4zdLEIykCcy8NZ16mMTZ7qXqmPabXmjY4+aeIhFXf8b87ELPmG7zZwvdyfFg82c7hmNN8MFgTGBLu52QWb3umvAvmZRDrSET+it4sfPH1ikPdRBBCa0l7AUyUmIBzM0XXtVvC1iHCMXL7YQIDAQAB
Add TXT record postmaster._domainkey
Step 13: Configure Exim to use DKIM:
Exim configuration :
Edit Exim’s configuration file /etc/exim4/conf.d/main/02_exim4-config_options
add theses lines at top
DKIM_DOMAIN = tutorialspots.com DKIM_SELECTOR = postmaster DKIM_PRIVATE_KEY = /etc/opendkim/keys/tutorialspots.com/postmaster.private
Step 14: Restart Exim and OpenDKIM :
Restart Exim :
sudo systemctl restart exim4
Restart OpenDKIM:
sudo systemctl restart opendkim
Verify SMTP server:
root@tutorialspots ~ # telnet 127.0.0.1 25 Trying 127.0.0.1... Connected to 127.0.0.1. Escape character is '^]'. 220 Ubuntu-2204-jammy-amd64-base ESMTP Exim 4.95 Ubuntu Mon, 13 May 2024 08:36:07 +0000
