===== Setting up a Postfix + Dovecot mailserver =====
\\

==== Firewall ====

The following ports have to be opened in your firewall:

<code>
  25/tcp  # SMTP
  80/tcp  # HTTP (for autoconfiguration)
 443/tcp  # HTTPS (for autoconfiguration)
 587/tcp  # Submission
 993/tcp  # IMAP SSL
4190/tcp  # ManageSieve (for e-mail filters)
</code>
----
\\

==== MariaDB ====

> [[https://en.wikipedia.org/wiki/MariaDB|MariaDB]] is a community-developed fork of the [[https://en.wikipedia.org/wiki/MySQL|MySQL]] relational database management system intended to remain free under the GNU GPL.

Install the database server:

<code bash>
sudo apt install mariadb-server
</code>

Harden it:

<code bash>
sudo mysql_secure_installation
</code>

Use one file per InnoDB table:

<file bash /etc/mysql/my.cnf>
[mysqld]
innodb_file_per_table = 1
</file>

Restart the daemon:

<code bash>
sudo systemctl restart mariadb.service
</code>
\\

Create a database called ''mailserver'' and a user called ''mailuser'':

<code bash>
sudo mariadb
</code>

<code sql>
CREATE DATABASE mailserver;
GRANT SELECT ON mailserver.* TO 'mailuser'@'localhost' IDENTIFIED BY 'password';
FLUSH PRIVILEGES;
USE mailserver;
</code>

(Of course, change ''password'' to an actual password.)\\
\\

=== Create tables ===

Domains:

<code sql>
CREATE TABLE `virtual_domains` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(50) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
</code>

Users:

<code sql>
CREATE TABLE `virtual_users` (
  `id` int(11) NOT NULL auto_increment,
  `domain_id` int(11) NOT NULL,
  `password` varchar(106) NOT NULL,
  `email` varchar(100) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `email` (`email`),
  FOREIGN KEY (domain_id) REFERENCES virtual_domains(id) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
</code>

Aliases:

<code sql>
CREATE TABLE `virtual_aliases` (
  `id` int(11) NOT NULL auto_increment,
  `domain_id` int(11) NOT NULL,
  `source` varchar(100) NOT NULL,
  `destination` varchar(100) NOT NULL,
  PRIMARY KEY (`id`),
  FOREIGN KEY (domain_id) REFERENCES virtual_domains(id) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
</code>
\\

=== Add domains, users, aliases ===

Domains:

<code sql>
INSERT INTO `mailserver`.`virtual_domains`
  (`id` ,`name`)
VALUES
  ('1', 'quietlife.nl');
</code>

Users:

<code sql>
INSERT INTO `mailserver`.`virtual_users`
  (`id`, `domain_id`, `password` , `email`)
VALUES
  ('1', '1', ENCRYPT('user1-password', CONCAT('$6$', SUBSTRING(SHA(RAND()), -16))), 'user1@quietlife.nl'),
  ('2', '1', ENCRYPT('user2-password', CONCAT('$6$', SUBSTRING(SHA(RAND()), -16))), 'user2@quietlife.nl');
</code>

Aliases:

<code sql>
INSERT INTO `mailserver`.`virtual_aliases`
  (`id`, `domain_id`, `source`, `destination`)
VALUES
  ('1', '1', 'postmaster@quietlife.nl', 'root@quietlife.nl'),
  ('2', '1', 'root@quietlife.nl', 'user1@quietlife.nl');
</code>

----
\\

==== Postfix ====

> [[https://en.wikipedia.org/wiki/Postfix_(software)|Postfix]] is a free and open-source [[https://en.wikipedia.org/wiki/Mail_transfer_agent|mail transfer agent]] (MTA) that routes and delivers electronic mail, intended as an alternative to Sendmail MTA.

<code bash>
sudo apt install postfix postfix-mysql
</code>

\\

<file bash /etc/postfix/main.cf>
smtpd_banner = $myhostname ESMTP
biff = no
append_dot_mydomain = no
readme_directory = no
compatibility_level = 2

# TLS parameters
smtp_dns_support_level = dnssec
smtp_tls_cert_file = /etc/letsencrypt/live/quietlife.nl/fullchain.pem
smtp_tls_key_file = /etc/letsencrypt/live/quietlife.nl/privkey.pem
smtp_tls_security_level = dane
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

smtpd_tls_auth_only = yes
smtpd_tls_cert_file = /etc/letsencrypt/live/quietlife.nl/fullchain.pem
smtpd_tls_key_file = /etc/letsencrypt/live/quietlife.nl/privkey.pem
smtpd_tls_security_level = may
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_tls_received_header = yes

# Use strong ciphers
smtp_tls_ciphers = high
smtp_tls_mandatory_ciphers = high

smtpd_tls_ciphers = high
smtpd_tls_mandatory_ciphers = high
smtpd_tls_eecdh_grade = ultra
smtpd_tls_dh1024_param_file = /etc/ssl/dhparams.pem

tls_preempt_cipherlist = yes
tls_ssl_options = NO_COMPRESSION, NO_RENEGOTIATION

# Enable SMTP for authenticated users and hand off authentication to Dovecot
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes
smtpd_recipient_restrictions =
	permit_sasl_authenticated,
	permit_mynetworks,
	reject_unauth_destination,
	reject_unauth_pipelining

# Network and host parameters
inet_interfaces = all
inet_protocols = all
mydestination = localhost
myhostname = vitas.quietlife.nl
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
myorigin = /etc/mailname

# Mail queue parameters
maximal_queue_lifetime = 12h
bounce_queue_lifetime = 12h
maximal_backoff_time = 1h
minimal_backoff_time = 5m
queue_run_delay = 5m

# Mailbox parameters
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
recipient_delimiter = +
disable_vrfy_command = yes

# Hand off local delivery to Dovecot's LMTP and tell it where to store mail
virtual_transport = lmtp:unix:private/dovecot-lmtp

# Virtual domains, users and aliases
virtual_mailbox_domains = mysql:/etc/postfix/mysql-virtual-mailbox-domains.cf
virtual_mailbox_maps = mysql:/etc/postfix/mysql-virtual-mailbox-maps.cf
virtual_alias_maps = mysql:/etc/postfix/mysql-virtual-alias-maps.cf, mysql:/etc/postfix/mysql-virtual-email2email.cf

# Strip MUA headers
smtp_header_checks = regexp:/etc/postfix/header_checks
</file>

<file bash /etc/mailname>
quietlife.nl
</file>

<file bash /etc/postfix/mysql-virtual-mailbox-domains.cf>
user = mailuser
password = password
hosts = 127.0.0.1
dbname = mailserver
query = SELECT 1 FROM virtual_domains WHERE name='%s'
</file>

<file bash /etc/postfix/mysql-virtual-mailbox-maps.cf>
user = mailuser
password = password
hosts = 127.0.0.1
dbname = mailserver
query = SELECT 1 FROM virtual_users WHERE email='%s'
</file>

<file bash /etc/postfix/mysql-virtual-alias-maps.cf>
user = mailuser
password = password
hosts = 127.0.0.1
dbname = mailserver
query = SELECT destination FROM virtual_aliases WHERE source='%s'
</file>

<file bash /etc/postfix/mysql-virtual-email2email.cf>
user = mailuser
password = password
hosts = 127.0.0.1
dbname = mailserver
query = SELECT email FROM virtual_users WHERE email='%s'
</file>

<file bash /etc/postfix/master.cf>
# ==========================================================================
# service   type  private unpriv  chroot  wakeup  maxproc command + args
#                 (yes)   (yes)   (no)    (never) (100)
# ==========================================================================
smtp        inet  n       -       y       -       -       smtpd
#smtp       inet  n       -       y       -       1       postscreen
#smtpd      pass  -       -       y       -       -       smtpd
#dnsblog    unix  -       -       y       -       0       dnsblog
#tlsproxy   unix  -       -       y       -       0       tlsproxy
submission  inet  n       -       y       -       -       smtpd
   -o syslog_name=postfix/submission
   -o smtpd_tls_security_level=encrypt
   -o smtpd_sasl_auth_enable=yes
   -o smtpd_client_restrictions=permit_sasl_authenticated,reject
   -o milter_macro_daemon_name=ORIGINATING
#  -o smtpd_reject_unlisted_recipient=no
#  -o smtpd_helo_restrictions=$mua_helo_restrictions
#  -o smtpd_sender_restrictions=$mua_sender_restrictions
#  -o smtpd_recipient_restrictions=
#  -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
#smtps      inet  n       -       y       -       -       smtpd
#  -o syslog_name=postfix/smtps
#  -o smtpd_tls_wrappermode=yes
#  -o smtpd_sasl_auth_enable=yes
#  -o smtpd_reject_unlisted_recipient=no
#  -o smtpd_client_restrictions=$mua_client_restrictions
#  -o smtpd_helo_restrictions=$mua_helo_restrictions
#  -o smtpd_sender_restrictions=$mua_sender_restrictions
#  -o smtpd_recipient_restrictions=
#  -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
#  -o milter_macro_daemon_name=ORIGINATING
#628        inet  n       -       y       -       -       qmqpd
pickup      unix  n       -       y       60      1       pickup
   -o content_filter=
   -o receive_override_options=no_header_body_checks
cleanup     unix  n       -       y       -       0       cleanup
qmgr        unix  n       -       n       300     1       qmgr
#qmgr       unix  n       -       n       300     1       oqmgr
tlsmgr      unix  -       -       y       1000?   1       tlsmgr
rewrite     unix  -       -       y       -       -       trivial-rewrite
bounce      unix  -       -       y       -       0       bounce
defer       unix  -       -       y       -       0       bounce
trace       unix  -       -       y       -       0       bounce
verify      unix  -       -       y       -       1       verify
flush       unix  n       -       y       1000?   0       flush
proxymap    unix  -       -       n       -       -       proxymap
proxywrite  unix  -       -       n       -       1       proxymap
smtp        unix  -       -       y       -       -       smtp
relay       unix  -       -       y       -       -       smtp
#  -o smtp_helo_timeout=5 -o smtp_connect_timeout=5
showq       unix  n       -       y       -       -       showq
error       unix  -       -       y       -       -       error
retry       unix  -       -       y       -       -       error
discard     unix  -       -       y       -       -       discard
local       unix  -       n       n       -       -       local
virtual     unix  -       n       n       -       -       virtual
lmtp        unix  -       -       y       -       -       lmtp
anvil       unix  -       -       y       -       1       anvil
scache      unix  -       -       y       -       1       scache
</file>

<file bash /etc/postfix/header_checks>
/^Received:.*with ESMTPSA/	IGNORE
/^X-Originating-IP:/		IGNORE
</file>

----
\\
==== Dovecot ====

> [[https://en.wikipedia.org/wiki/Dovecot_(software)|Dovecot]] is an open-source IMAP and POP3 server for Linux/UNIX-like systems, written primarily with security in mind.

<code bash>
sudo apt install dovecot-core dovecot-imapd dovecot-lmtpd dovecot-mysql dovecot-sieve dovecot-managesieved dovecot-antispam
</code>

Create a ''vmail'' user and ''vmail'' group and set permissions:

<code bash>
sudo groupadd -g 5000 vmail
sudo useradd -g vmail -u 5000 vmail -d /var/mail
sudo chown -R vmail:vmail /var/mail
sudo mkdir -p /var/mail/vhosts/quietlife.nl
sudo chmod 2700 /var/mail/vhosts/*
sudo chown -R vmail:dovecot /etc/dovecot
</code>
\\

<file bash /etc/dovecot/dovecot.conf>
# Enable installed protocols
!include_try /usr/share/dovecot/protocols.d/*.protocol
protocols = imap lmtp
</file>

<file bash /etc/dovecot/conf.d/10-mail.conf>
# Location for users' mailboxes.
mail_location = maildir:/var/mail/vhosts/%d/%n

[...]

# System user and group used to access mails.
mail_uid = vmail
mail_gid = vmail

# Group to enable temporarily for privileged operations.
mail_privileged_group = vmail

[...]

# Space separated list of plugins to load for all services. Plugins specific to
# IMAP, LDA, etc. are added to this list in their own .conf files.
mail_plugins = $mail_plugins antispam quota
</file>

<file bash /etc/dovecot/conf.d/10-auth.conf>
# Disable LOGIN command and all other plaintext authentications unless
# SSL/TLS is used (LOGINDISABLED capability).
disable_plaintext_auth = yes

[...]

# Space separated list of wanted authentication mechanisms:
auth_mechanisms = plain login

[...]

## Password and user databases
##
#!include auth-system.conf.ext
!include auth-sql.conf.ext
</file>

<file bash /etc/dovecot/conf.d/auth-sql.conf.ext>
passdb {
  driver = sql
  args = /etc/dovecot/dovecot-sql.conf.ext
}

[...]

userdb {
  driver = static
  args = uid=vmail gid=vmail home=/var/mail/vhosts/%d/%n
}
</file>

<file bash /etc/dovecot/dovecot-sql.conf.ext>
# Database driver: mysql, pgsql, sqlite
driver = mysql

[...]

# Database connection string. This is driver-specific setting.
connect = host=localhost dbname=mailserver user=mailuser password=password

[...]

# Default password scheme.
default_pass_scheme = SHA512-CRYPT

[...]

# passdb query to retrieve the password.
password_query = SELECT email as user, password FROM virtual_users WHERE email='%u';
</file>

<file bash /etc/dovecot/conf.d/10-master.conf>
# Enable imaps on port 993 only (disable imap on port 143)
service imap-login {
  inet_listener imap {
    port = 0
  }
  inet_listener imaps {
    port = 993
    ssl = yes
  }

[...]

# Disable pop3s and pop3
service pop3-login {
  inet_listener pop3 {
    port = 0
  }
  inet_listener pop3s {
    port = 0
    #ssl = yes
  }
}

# Enable lmtp for local delivery
service lmtp {
  unix_listener /var/spool/postfix/private/dovecot-lmtp {
    mode = 0600
    user = postfix
    group = postfix
  }
}

[...]

service auth {
  unix_listener auth-userdb {
    mode = 0600
    user = vmail
    group = vmail
  }

  # Postfix smtp-auth
  unix_listener /var/spool/postfix/private/auth {
    mode = 0666
    user = postfix
    group = postfix
  }

  # Auth process is run as this user.
  user = dovecot
}

service auth-worker {
  user = vmail
}
</file>

<file bash /etc/dovecot/conf.d/10-ssl.conf>
# SSL/TLS support: yes, no, required.
ssl = required

[...]

# PEM encoded X.509 SSL/TLS certificate and private key.
ssl_cert = </etc/letsencrypt/live/quietlife.nl/fullchain.pem 
ssl_key = </etc/letsencrypt/live/quietlife.nl/privkey.pem

[...]

# Minimum SSL protocol version to use.
ssl_min_protocol = TLSv1.2

# SSL ciphers to use
ssl_cipher_list = EECDH+AESGCM:EDH+AESGCM

# Colon separated list of elliptic curves to use. Empty value (the default)
# means use the defaults from the SSL library. P-521:P-384:P-256 would be an
# example of a valid value.
ssl_curve_list = P-521:P-384

# Prefer the server's order of ciphers over client's
ssl_prefer_server_ciphers = yes 
</file>

Automatically create default mailboxes:

<file bash /etc/dovecot/conf.d/15-mailboxes.conf>
namespace inbox {
  mailbox Drafts {
    auto = subscribe
    special_use = \Drafts
  }
  mailbox Junk {
    auto = subscribe
    special_use = \Junk
  }
  mailbox Trash {
    auto = subscribe
    special_use = \Trash
  }

  [...]

  mailbox Sent {
    auto = subscribe
    special_use = \Sent
  }

  [...]

}
</file>

Enable ManageSieve so users can set up filters:

<file bash /etc/dovecot/conf.d/20-managesieve.conf>
# Uncomment to enable managesieve protocol:
protocols = $protocols sieve

# Service definitions

service managesieve-login {
  inet_listener sieve {
    port = 4190
  }

[...]
}
</file>

<file bash /etc/dovecot/conf.d/20-lmtp.conf>
[...]

protocol lmtp {
  # Space separated list of plugins to load (default is global mail_plugins).
  mail_plugins = $mail_plugins sieve
}
</file>

----
\\
==== Sender Policy Framework ====

> [[https://en.wikipedia.org/wiki/Sender_Policy_Framework|Sender Policy Framework]] (SPF) is a simple email-validation system designed to detect email spoofing by providing a mechanism to allow receiving mail exchangers to check that incoming mail from a domain comes from a host authorized by that domain's administrators.

<code bash>
sudo apt install postfix-pcre postfix-policyd-spf-python
</code>
\\

Add SPF to the Postfix configuration:

Change

<file bash /etc/postfix/main.cf>
smtpd_recipient_restrictions = 
	permit_sasl_authenticated, 
	permit_mynetworks, 
	reject_unauth_destination,
	reject_unauth_pipelining
</file>

to

<file bash /etc/postfix/main.cf>
smtpd_recipient_restrictions = 
	permit_sasl_authenticated, 
	permit_mynetworks, 
	reject_unauth_destination,
	reject_unauth_pipelining,
	check_policy_service unix:private/policyd-spf

policyd-spf_time_limit = 3600
</file>

(Mind the comma!)

<file bash /etc/postfix/master.cf>
[...]

# SPF configuration
policyd-spf unix  -       n       n       -       0       spawn
  user=policyd-spf argv=/usr/bin/policyd-spf
</file>
\\

Finally, add a DNS TXT record for ''@'' (or ''quietlife.nl.''), containing:

<code bash>
"v=spf1 mx -all"
</code>

This tells the receiving mailserver that all mails coming from your domain should originate from the IP's in your A / AAAA records. 

----
\\

==== OpenDKIM ====

> [[https://en.wikipedia.org/wiki/DomainKeys_Identified_Mail|DomainKeys Identified Mail]] (DKIM) is an email authentication method designed to detect email spoofing. It allows the receiver to check that an email claimed to have come from a specific domain was indeed authorized by the owner of that domain.

<code bash>
sudo apt install opendkim opendkim-tools
</code>
\\

Add the ''opendkim'' user to the ''postfix'' group:

<code bash>
sudo adduser postfix opendkim
</code>
\\

Create an ''/etc/opendkim'' directory to store the tables:

<code bash>
sudo mkdir /etc/opendkim
</code>

<file bash /etc/opendkim.conf>
Syslog                  yes
SyslogSuccess           yes
LogWhy                  yes

Canonicalization        relaxed/simple
Mode                    sv
SubDomains              no
OversignHeaders         From

KeyTable                /etc/opendkim/key.table
SigningTable            refile:/etc/opendkim/signing.table 
ExternalIgnoreList      /etc/opendkim/trusted.hosts
InternalHosts           /etc/opendkim/trusted.hosts

UserID                  opendkim:postfix
UMask                   007

Socket                  local:/var/spool/postfix/var/run/opendkim/opendkim.sock
PidFile                 /var/spool/postfix/var/run/opendkim/opendkim.pid

TrustAnchorFile         /usr/share/dns/root.key
</file>

Change the ''201902'' example to the current year/month:

<file bash /etc/opendkim/key.table>
quietlife.nl    quietlife.nl:201902:/etc/dkimkeys/quietlife.nl.private
</file>

<file bash /etc/opendkim/signing.table>
*@quietlife.nl  quietlife.nl
</file>

Add localhost, your hostname, your domain name(s) and your FQDN to the trusted hosts:

<file bash /etc/opendkim/trusted.hosts>
127.0.0.1
::1
localhost
vitas
quietlife.nl
vitas.quietlife.nl
</file>
\\

Then override the OpenDKIM systemd unit file by running ''sudo systemctl edit opendkim.service''. Add these lines:

<code bash>
[Service]
PIDFile=/var/spool/postfix/var/run/opendkim/opendkim.pid
User=opendkim
Group=postfix
ExecStart=
ExecStart=/usr/sbin/opendkim -P /var/spool/postfix/var/run/opendkim/opendkim.pid -p local:/var/spool/postfix/var/run/opendkim/opendkim.sock
</code>

And run ''sudo systemctl daemon-reload'' afterwards.
\\
\\

Add OpenDKIM to the Postfix configuration:

<code bash>
sudo mkdir -p /var/spool/postfix/var/run/opendkim
sudo chown opendkim:postfix /var/spool/postfix/var/run/opendkim
</code>

<file bash /etc/postfix/main.cf>
[...]

# Use OpenDKIM to sign and verify mail
milter_default_action = accept
milter_protocol = 6
smtpd_milters = unix:var/run/opendkim/opendkim.sock
non_smtpd_milters = $smtpd_milters
</file>
\\

Generate keys (use the current year/month instead of the example ''201902''):

<code bash>
opendkim-genkey -b 2048 -h rsa-sha256 -r -s 201902 -d quietlife.nl -v
sudo mv 201902.private /etc/dkimkeys/quietlife.nl.private
sudo chown opendkim:opendkim /etc/dkimkeys/quietlife.nl.private
mv 201902.txt dns.txt
</code>
\\

Finally, add a DNS TXT record with the contents of ''dns.txt'':

<code bash>
201902._domainkey  3600  IN  TXT  "v=DKIM1; h=sha256; k=rsa; s=email; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA63ggTqo80JaQBGV2uNreiX2/2yQx3PHbh9/4k+gIYO71ujqjGblk5z2FgzbWrTaIU7fZ0nN09bZAVDYavc9817fpYIYvnenDdKPJazl4hiVbBJL8jZ8/0ndu5WkCIzY60ukI423IAK+ppx7UW7Tpq38RokyFW8Wq96RAuhqeGkdxQN03N//yAtRCmeWwHw+jdGGq1WGbOKE7LcigRBMW9xPdJOk/rQPU2OjRh3b/BLohMYY0NX+0+Ybp0+5JuO6NZeYqWKbvezhtltTPrsYJU1m3cJTv11UxYiI8QPmSPGMJKVUevQv6Pn2aCARuNPIxSqfGwW6iwBhUZuxb1zQPCwIDAQAB"
</code>

(Change ''h=rsa-sha256'' to ''h=sha256'' and cut the key starting with ''v=DKIM1; ...'')

----
\\
==== Amavis ====

> [[https://en.wikipedia.org/wiki/Amavis|Amavis]] is an open source content filter for electronic mail, implementing mail message transfer, decoding, some processing and checking, and interfacing with external content filters to provide protection against spam, viruses and other malware.

<code bash>
sudo apt install amavisd-new spamassassin libmail-spf-perl pyzor razor p7zip-full unbound
</code>

Set up razor:

<code bash>
sudo su - amavis -s /bin/bash
razor-admin -create
razor-admin -register
exit
</code>

<file bash /etc/amavis/conf.d/05-node_id>
# To manually set $myhostname, edit the following line with the correct Fully
# Qualified Domain Name (FQDN) and remove the # at the beginning of the line.
$myhostname = "localhost";
</file>

Enable spam filtering:

<file bash /etc/amavis/conf.d/15-content_filter_mode>
# Default SPAM checking mode
# Please note, that anti-spam checking is DISABLED by
# default.
# If You wish to enable it, please uncomment the following lines:
@bypass_spam_checks_maps = (
   \%bypass_spam_checks, \@bypass_spam_checks_acl, \$bypass_spam_checks_re);
</file>

<file bash /etc/amavis/conf.d/50-user>
$undecipherable_subject_tag = undef;
$virus_admin = undef;
$spam_admin = undef;

$final_spam_destiny = D_DISCARD;
</file>

Add Amavis to the Postfix configuration:

<file bash /etc/postfix/main.cf>
[...]

# Use Amavis to filter content
content_filter = smtp-amavis:localhost:10024
</file>

<file bash /etc/postfix/master.cf>
[...]

# Amavis configuration
smtp-amavis unix  -       -       -       -       2       smtp
   -o smtp_data_done_timeout=1200
   -o smtp_send_xforward_command=yes
   -o disable_dns_lookups=yes
   -o max_use=20
localhost:10025 inet n    -       -       -       -       smtpd
   -o content_filter=
   -o local_recipient_maps=
   -o relay_recipient_maps=
   -o smtpd_restriction_classes=
   -o smtpd_delay_reject=no
   -o smtpd_client_restrictions=permit_mynetworks,reject
   -o smtpd_helo_restrictions=
   -o smtpd_sender_restrictions=
   -o smtpd_recipient_restrictions=permit_mynetworks,reject
   -o smtpd_data_restrictions=reject_unauth_pipelining
   -o smtpd_end_of_data_restrictions=
   -o mynetworks=127.0.0.0/8,[::ffff:127.0.0.0]/104,[::1]/128
   -o smtpd_error_sleep_time=0
   -o smtpd_soft_error_limit=1001
   -o smtpd_hard_error_limit=1000
   -o smtpd_client_connection_count_limit=0
   -o smtpd_client_connection_rate_limit=0
   -o receive_override_options=no_header_body_checks,no_unknown_recipient_checks,no_milters
</file>

Delete quarantined mails older than a month:

<code bash>
sudo -u amavis crontab -e

0 0 * * * find /var/lib/amavis/virusmails/ -mtime +31 -type f -delete &>/dev/null
</code>

Automatically move flagged spam mails to the ''Junk'' directory:

<code bash>
sudo mkdir /var/lib/dovecot/sieve
sudo chown dovecot:dovecot /var/lib/dovecot/sieve
</code>

<file bash /var/lib/dovecot/sieve/spam_to_junk.sieve>
require "fileinto";

if exists "X-Spam-Score" {
    fileinto "Junk";
    stop;
}
</file>

<code bash>
sudo sievec /var/lib/dovecot/sieve/spam_to_junk.sieve
sudo chown dovecot:dovecot /var/lib/dovecot/sieve/*
</code>

<file bash /etc/dovecot/conf.d/90-sieve.conf>
[...]
Location for ":global" include scripts as used by the "include" extension.
sieve_global = /var/lib/dovecot/sieve/
[...]
</file>

Train SpamAssassin when moving files to and from the junk directory:

<file bash /etc/dovecot/conf.d/90-plugin.conf>
plugin {
  #setting_name = value
  antispam_debug_target = syslog
  antispam_backend = pipe
  antispam_trash = Trash
  antispam_spam = Junk;Spam
  antispam_allow_append_to_spam = no
  antispam_pipe_program = /usr/local/bin/sa-learn-pipe.sh
  antispam_pipe_program_spam_arg = --spam
  antispam_pipe_program_notspam_arg = --ham
}
</file>

<file bash /usr/local/bin/sa-learn-pipe.sh>
#!/bin/bash

if [ "$1" != "wrap" ]; then
        out=$(sudo -Hu amavis "$0" wrap "$@" < /proc/self/fd/0 2>&1)
        ret=$?
        lvl="info"
        if [ "$ret" -ne 0 ]; then
                lvl="err"
        fi
        logger -p mail.$lvl -i -t sa-learn-pipe "${1//[^a-z]/}: $out"
        exit $ret
fi

cd "$HOME"

cmd=${2//[^a-z\- ]/}

sa-learn "$cmd" <(cat -)
ret=$?
exit $ret
</file>

Make it executable:

<code bash>
sudo chmod +x /usr/local/bin/sa-learn-pipe.sh
</code>

Allow the ''vmail'' user to execute the script as the ''amavis'' user:

<file bash /etc/sudoers.d/vmail-sa-learn>
vmail ALL=(amavis) NOPASSWD: /usr/local/bin/sa-learn-pipe.sh
</file>

Set the correct permissions:

<code bash>
sudo chmod 400 /etc/sudoers.d/vmail-sa-learn
</code>

----
\\

==== Fail2Ban ====

> Fail2Ban is an intrusion prevention software framework. Written in the Python programming language, it is designed to prevent brute-force attacks. It is able to run on POSIX systems that have an interface to a packet-control system or firewall installed locally, such as iptables or TCP Wrapper.

<code bash>
sudo apt install fail2ban
</code>

Create the configuration file for Postfix, Dovecot and Sieve:

<file bash /etc/fail2ban/jail.d/mail.conf>
[postfix]
enabled  = true
mode     = aggressive
backend  = auto

[dovecot]
enabled  = true
mode     = aggressive
backend  = auto

[sieve]
enabled  = true
backend  = auto
</file>

\\

==== Client autoconfiguration ====

> The goal of [[https://developer.mozilla.org/docs/Mozilla/Thunderbird/Autoconfiguration|autoconfiguration]] is to make it very easy for users to configure the connection to their email servers.

This guide assumes you use Apache or nginx, but any HTTP server will suffice.

The result is an autoconfiguration URL that mail clients like Thunderbird can parse to preconfigure settings.

=== Apache ===

<file apache /etc/apache2/sites-available/autoconfig.quietlife.nl.conf>
<VirtualHost *:80>
   ServerName autoconfig.quietlife.nl
   DocumentRoot /var/www/autoconfig.quietlife.nl
    <Directory /var/www/autoconfig.quietlife.nl>
     Order allow,deny
     allow from all
    </Directory>
</VirtualHost>
</file>

Enable it:

<code bash>
sudo a2ensite autoconfig.quietlife.nl.conf
sudo systemctl reload apache2.service
</code>
\\

=== nginx ===

<file nginx /etc/nginx/sites-available/autoconfig.quietlife.nl>
server {
        listen 80;
        listen [::]:80;
        server_name autoconfig.quietlife.nl;
        root /var/www/autoconfig.quietlife.nl;
}
</file>

Enable it:

<code bash>
cd /etc/nginx/sites-enabled/
sudo ln -s ../sites-available/autoconfig.quietlife.nl autoconfig.quietlife.nl
sudo systemctl reload nginx.service
</code>
\\

=== Configuration ===

<file xml /var/www/autoconfig.quietlife.nl/mail/config-v1.1.xml>
<?xml version="1.0" encoding="UTF-8"?>
<clientConfig version="1.1">
 <emailProvider id="quietlife.nl">
  <domain>quietlife.nl</domain>
  <displayName>quietlife.nl</displayName>
  <displayShortName>quietlife</displayShortName>
   <incomingServer type="imap">
    <hostname>quietlife.nl</hostname>
    <port>993</port>
    <socketType>SSL</socketType>
    <authentication>password-cleartext</authentication>
    <username>%EMAILADDRESS%</username>
   </incomingServer>
   <outgoingServer type="smtp">
    <hostname>quietlife.nl</hostname>
    <port>587</port>
    <socketType>STARTTLS</socketType>
    <authentication>password-cleartext</authentication>
    <username>%EMAILADDRESS%</username>
   </outgoingServer>
 </emailProvider>
</clientConfig>
</file>

----
\\

==== SSL certificate renewal ====

Let's Encrypt certificates expire every three months, and certbot automatically renews them. After renewing the certificates, you have to reload Postfix and Dovecot. This can be automated with a script you put in ''/etc/letsencrypt/renewal-hooks/post/'':

<code bash /etc/letsencrypt/renewal-hooks/post/mail.sh>
#!/bin/sh
systemctl reload dovecot.service postfix.service
</code>

Make it executable:

<code bash>
sudo chmod +x /etc/letsencrypt/renewal-hooks/post/mail.sh
</code>

----
\\

==== Starting everything up ====

<code bash>
sudo systemctl restart postfix.service dovecot.service opendkim.service amavis.service fail2ban.service
</code>
----

\\

==== Testing ====

> [[https://en.wikipedia.org/wiki/Failure|Failure]] is the state or condition of not meeting a desirable or intended objective, and may be viewed as the opposite of success.

=== Test your mail server status ===

Go to [[https://mxtoolbox.com/domain/|MxToolBox]] and run a test. Ideally, you should not see any problems.\\
\\

=== Test DKIM DNS record ===

<code bash>
opendkim-testkey -d quietlife.nl -s 201902
</code>

If nothing is shown, your DNS record is set up properly.\\
\\

=== Test signatures ===

Send an empty email to [[check-auth@verifier.port25.com|port25.com's verifier]]. It should return this:

<code>
==========================================================
Summary of Results
==========================================================
SPF check:          pass
DKIM check:         pass
SpamAssassin check: ham
</code>

----
\\

==== Author Domain Signing Practices ====

> In computing, [[https://en.wikipedia.org/wiki/Author_Domain_Signing_Practices|Author Domain Signing Practices]] (ADSP) is an optional extension to the DKIM email authentication scheme, whereby a domain can publish the signing practices it adopts when relaying mail on behalf of associated authors.

If DKIM is working well, you can set up an ADSP record, telling the receiving mailserver that all mails coming from your domain should have a valid DKIM signature.

Add a DNS TXT record containing this:

<code bash>
_adsp._domainkey  3600  IN  TXT  "dkim=all"
</code>

----
\\

==== Domain-based Message Authentication, Reporting & Conformance ====

> [[https://en.wikipedia.org/wiki/DMARC|Domain-based Message Authentication, Reporting and Conformance]] (DMARC) is an email-validation system designed to detect and prevent email spoofing. It is intended to combat certain techniques often used in phishing and email spam, such as emails with forged sender addresses that appear to originate from legitimate organizations.

If SPF and DKIM are working well, you can set up a DMARC record.

Add a DNS TXT record containing this: 

<code bash>
_dmarc  3600  IN  TXT  "v=DMARC1; p=reject"
</code>
\\

If you want to receive aggregate reports, you can set a ''rua'' option:

<code bash>
_dmarc  3600  IN  TXT  "v=DMARC1; p=reject; rua=mailto:postmaster@quietlife.nl"
</code>


If you also want to receive failure reports, you can set a ''ruf'' option:

<code bash>
_dmarc  3600  IN  TXT  "v=DMARC1; p=reject; rua=mailto:postmaster@quietlife.nl; ruf=mailto:postmaster@quietlife.nl"
</code>
\\

More information about DMARC records can be found [[https://dmarc.org/wiki/FAQ|here]].

----