SimpleMailServerOnUbuntu: Mail Server with SMTP and IMAP on Ubuntu 20.04
Copyright (C) 2020 Exforge exforge@x386.xyz
# This document is free text: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# any later version.
# This document is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
# Based on the valuable documents at:
https://www.server-world.info/en/note?os=Ubuntu_18.04&p=mail&f=1
# SMTP: Postfix
# IMAP: Dovecot
# No virtual domains, only Linux users will have email accounts
# Tried to be as simple as possible
#
# Hostname: mail.x11.xyz
# Mail Domain: x11.xyz
#
# An MX record must be created at the DNS Server with the value of mail.x11.xyz
1. Install and Configure Postfix
# 1.1. Install Postfix and SASL (Simple Auth. & Security Layer)
sudo apt -y install postfix sasl2-bin
# Select No configuration at the install question, we will configure manually
#
# 1.2. Create a standart config file for postfix
sudo cp /usr/share/postfix/main.cf.dist /etc/postfix/main.cf
#
# 1.3. Edit postfix config file as described
sudo nano /etc/postfix/main.cf
#
# around line 78: uncomment
mail_owner = postfix
#
# around line 94: uncomment and specify hostname
myhostname = mail.x11.xyz
#
# around line 102: uncomment and specify domainname
mydomain = x11.xyz
#
# around line 123: uncomment
myorigin = $mydomain
#
# around line 137: uncomment
inet_interfaces = all
#
# around line 185: uncomment
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
#
# around line 228: uncomment
local_recipient_maps = unix:passwd.byname $alias_maps
#
# around line 270: uncomment
mynetworks_style = subnet
#
# around line 287: add your local network
mynetworks = 127.0.0.0/8, 10.0.0.0/24
#
# around line 407: uncomment
alias_maps = hash:/etc/aliases
#
# around line 418: uncomment
alias_database = hash:/etc/aliases
#
# around line 440: uncomment
home_mailbox = Maildir/
#
# around line 576: comment out and add
#smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
smtpd_banner = $myhostname ESMTP
#
# around line 650: add
sendmail_path = /usr/sbin/postfix
#
# around line 655: add
newaliases_path = /usr/bin/newaliases
#
# around line 660: add
mailq_path = /usr/bin/mailq
#
# around line 666: add
setgid_group = postdrop
#
# around line 670: comment out
#html_directory =
#
# around line 674: comment out
#manpage_directory =
#
# around line 679: comment out
#sample_directory =
#
# around line 683: comment out
#readme_directory =
#
# add to the end:
# limit an email size 10M
message_size_limit = 10485760
# limit mailbox 1G
mailbox_size_limit = 1073741824
# SMTP-Auth setting
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain = $myhostname
smtpd_recipient_restrictions = permit_mynetworks, permit_auth_destination, permit_sasl_authenticated, reject
#
# 1.4. Activate Aliases (Will be explained at 5.2.)
sudo newaliases
# 1.5. Restart Postfix
sudo systemctl restart postfix
2. Install and Configure Dovecot
# 2.1. Install Dovecot core, pop3 and imap deamons
sudo apt -y install dovecot-core dovecot-pop3d dovecot-imapd
#
# 2.2. Dovecot main config
sudo nano /etc/dovecot/dovecot.conf
# around line 30: uncomment
listen = *, ::
#
# 2.3. Dovecot auth config
sudo nano /etc/dovecot/conf.d/10-auth.conf
# around line 10: uncomment and change ( allow plain text auth )
disable_plaintext_auth = no
#
# around line 100: add
auth_mechanisms = plain login
#
# 2.4. Dovecot mail config
sudo nano /etc/dovecot/conf.d/10-mail.conf
# around line 30: change to Maildir
mail_location = maildir:~/Maildir
#
# 2.5. Dovecot master config
sudo nano /etc/dovecot/conf.d/10-master.conf
# around line 107-109: uncomment and add
# Postfix smtp-auth
unix_listener /var/spool/postfix/private/auth {
mode = 0666
user = postfix
group = postfix
}
#
# 2.6. Restart Dovecot
sudo systemctl restart dovecot
# At this point we have a very basic mail config, all our linux users at
# mail.x11.xyz have mail addresses. They can access smtp at port 25 and imap at
# port 143. But unfortunately there is no encryption.
# At the next step we will add SSL encrytpion and that will change our smtp port to 587.
#
# The easiest way to get SSL certificate for our mail server is:
# Install apache2
# Create a site with servername mail.x11.xyz
# Get ssl certificate with Certbot
# (See tutorial CertbotOnUbuntu)
# At the next section I assume you have certificates as
# /etc/letsencrypt/live/mail.x11.xyz/fullchain.pem
# /etc/letsencrypt/live/mail.x11.xyz/privkey.pem
3. Add SSL/TLS to Postfix and Dovecot
# 3.1. Postfix main config
sudo nano /etc/postfix/main.cf
# Add to the end
smtpd_use_tls = yes
smtp_tls_mandatory_protocols = !SSLv2, !SSLv3
smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3
smtpd_tls_cert_file = /etc/letsencrypt/live/mail.x11.xyz/fullchain.pem
smtpd_tls_key_file = /etc/letsencrypt/live/mail.x11.xyz/privkey.pem
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
#
# 3.2. Postfix master config
sudo nano /etc/postfix/master.cf
# Around line 17-21: uncomment like follows
submission inet n - y - - smtpd
-o syslog_name=postfix/submission
# -o smtpd_tls_security_level=encrypt
-o smtpd_sasl_auth_enable=yes
-o smtpd_tls_auth_only=yes
# Around line 29-31: uncomment like follows
smtps inet n - y - - smtpd
-o syslog_name=postfix/smtps
-o smtpd_tls_wrappermode=yes
#
# 3.3. Dovecot config
sudo nano /etc/dovecot/conf.d/10-ssl.conf
# Around line 12,13: Specify certificates (change as below)
# Remember to change domain names:
ssl_cert = </etc/letsencrypt/live/mail.x11.xyz/fullchain.pem
ssl_key = </etc/letsencrypt/live/mail.x11.xyz/privkey.pem
#
# 3.4. Restart Postfix and Dovecot
sudo systemctl restart postfix dovecot
# For Linux User exforge at mail.x11.xyz
# Replace all occurences of:
# exforge --> your user name
# mail.x11.xyz --> your server name
# x11.xyz --> your domain
#
# Thunderbird Config:
# Your name: Exforge
# Email address: exforge@x11.xyz
# Password: (Your Linux Password)
# Incoming: IMAP mail.x11.xyz 143 STARTTLS Normal password
# Outgoing: SMTP mail.x11.xyz 465 SSL/TLS Normal password
# Username: Incoming: exforge Outgoing: exforge
#
# See my config screenshot at:
https://imgur.com/a/RVIAy3o
# 5.1. All Linux users already have mail accounts with their login name and passwords.
# To add a new mail user, you need to add a user to your server
sudo useradd -d /home/exforge -m exforge
# And you need to give her a password too
sudo passwd exforge
#
# 5.2. If you want to use aliases, say postmaster and abuse for user exforge.
# First create Linux users
sudo useradd -d /home/postmaster -m postmaster
sudo useradd -d /home/abuse -m abuse
sudo passwd postmaster
sudo passwd abuse
# Add them to /etc/aliases file
sudo nano /etc/aliases
#_______________________________________
# See man 5 aliases for format
postmaster: exforge
abuse: exforge
#_______________________________________
#
# Activate aliases
sudo newaliases
#
# 5.3. Restart Postfix and Dovecot
sudo systemctl restart postfix dovecot