Email server setup
Contents
Overview
Requirements
An email server requires a lot of components:
- Send / Receive emails [SMTP, POP3, IMAP, ...]
- Tools to check the email content against virus, spam
- Tools to encrypt the communication
- (optional) Database to manage users and emails
Therefore, before going on you need to have:
- MySQL server
- MySQL client such as MySQL workbench
Setup
Create Linux mail user
It's a common good practice to create a dedicated user to send email. That's the user POSTFIX will use.
As usual in Linux, that user should be UID > 1000 so it has more restrictions.
# Server root folder, where all the mails will be stored
mkdir -p /var/spool/mail/virtualMail
# New user
groupadd --system virtualMail -g 5000
useradd --system virtualMail -u 5000 -g 5000
chown -R virtualMail:virtualMail /var/spool/mail/virtualMail
MySQL database
Create and initialize a new database and user for email.
Create database
I assume that:
- Database name: maildb
- Db user: maildb
# log in as root
mysql -u root -p
# Create the mail database
create database maildb;
# Create a new user and grant rights upon mail database
GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP ON maildb.* TO 'mail'@'localhost' IDENTIFIED by 'mailPASSWORD';
GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP ON maildb.* TO 'mail'@'%' IDENTIFIED by 'mailPASSWORD';
exit;
Schema
Create the following schema using MySQL workbench:
CREATE TABLE `aliases` (
`pkid` smallint(3) NOT NULL auto_increment,
`mail` varchar(120) NOT NULL default '',
`destination` varchar(120) NOT NULL default '',
`enabled` tinyint(1) NOT NULL default '1',
PRIMARY KEY (`pkid`),
UNIQUE KEY `mail` (`mail`) ) ;
CREATE TABLE `domains` (
`pkid` smallint(6) NOT NULL auto_increment,
`domain` varchar(120) NOT NULL default '',
`transport` varchar(120) NOT NULL default 'virtual:',
`enabled` tinyint(1) NOT NULL default '1',
PRIMARY KEY (`pkid`) ) ;
CREATE TABLE `users` (
`id` varchar(128) NOT NULL default '',
`name` varchar(128) NOT NULL default '',
`uid` smallint(5) unsigned NOT NULL default '5000',
`gid` smallint(5) unsigned NOT NULL default '5000',
`home` varchar(255) NOT NULL default '/var/spool/mail/virtual',
`maildir` varchar(255) NOT NULL default 'blah/',
`enabled` tinyint(3) unsigned NOT NULL default '1',
`change_password` tinyint(3) unsigned NOT NULL default '1',
`clear` varchar(128) NOT NULL default 'ChangeMe',
`crypt` varchar(128) NOT NULL default 'sdtrusfX0Jj66',
`quota` varchar(255) NOT NULL default '',
PRIMARY KEY (`id`),
UNIQUE KEY `id` (`id`) ) ;
Source: http://flurdy.com/docs/postfix/
POSTFIX (SMTP server)
Installation
POSTFIX SMTP server:
apt-get install postfix postfix-mysql
mkdir -p /var/spool/mail/virtual
Basic configuration
vim /etc/postfix/mail.cf
Put the following configuration:
##########################
# MISC settings #
##########################
# Server name
smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no
# appending .domain is the MUA's job.
append_dot_mydomain = no
# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h
readme_directory = no
# Use external SMTP relay?
relayhost =
smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
# Bind interfaces
inet_interfaces = all
# Restrict to IPv4 (= avoid IPv6 errors and log spam)
inet_protocols=ipv4
###########################
# Email global settings #
###########################
# Email server name
myhostname = smartcard-mail.smartcards.vehco.com
# Domain name for emails originated from this server
#myorigin = /etc/mailname
myorigin = smartcards.vehco.com
# Local destination (= email server local alias)
mydestination = smartcard-mail.smartcards.vehco.com, localhost.smartcards.vehco.com, , localhost
# Trusted senders
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 172.16.50.0/24 172.16.60.0/24
##############################
# Commands #
##############################
mailbox_command = procmail -a "$EXTENSION"
###################################
# Email accounts / msg settings #
###################################
# Max mailbox size
mailbox_size_limit = 0
# Max number of mailboxes
virtual_mailbox_limit = 0
# Max message size
message_size_limit = 0
# Misc settings
recipient_delimiter = +
###########################
# Connection settings #
###########################
# how long to keep message on queue before return as failed
maximal_queue_lifetime = 1h
# max and min time in seconds between retries if connection failed
minimal_backoff_time = 5m
maximal_backoff_time = 10m
# how long to wait when servers connect before receiving rest of data
smtp_helo_timeout = 60s
# how many address can be used in one message.
# effective stopper to mass spammers, accidental copy in whole address list but may restrict intentional mail shots.
smtpd_recipient_limit = 16
# how many error before back off.
smtpd_soft_error_limit = 3
# how many max errors before blocking it.
smtpd_hard_error_limit = 12
####################################
# Security: protocol enforcement #
####################################
# Requirements for the HELO statement
smtpd_helo_restrictions = permit_mynetworks, warn_if_reject reject_non_fqdn_hostname, reject_invalid_hostname, permit
# Requirements for the sender details
smtpd_sender_restrictions = permit_mynetworks, warn_if_reject reject_non_fqdn_sender, reject_unknown_sender_domain, reject_unauth_pipelining, permit
# Requirements for the connecting server
smtpd_client_restrictions = reject_rbl_client sbl.spamhaus.org, reject_rbl_client blackholes.easynet.nl
# Requirement for the recipient address
smtpd_recipient_restrictions = reject_unauth_pipelining, permit_mynetworks, reject_non_fqdn_recipient, reject_unknown_recipient_domain, reject_unauth_destination, permit
smtpd_data_restrictions = reject_unauth_pipelining
# require proper helo at connections
smtpd_helo_required = yes
# waste spammers time before rejecting them
smtpd_delay_reject = yes
disable_vrfy_command = yes
############################
# Email accounts #
############################
# Alias definitions
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
# Location of the virtual mailbox folder (= Global server mailbox)
# ... This must match the folder you created in [[#Create Linux mail user]]
virtual_mailbox_base = /var/spool/mail/virtualMail
## MySQL settings
# Mailbox location for each user
virtual_mailbox_maps = mysql:/etc/postfix/mysql_mailbox.cf
# List of virtual mailboxes
virtual_alias_maps = mysql:/etc/postfix/mysql_alias.cf
# Domain lookups
virtual_mailbox_domains = mysql:/etc/postfix/mysql_domains.cf
############################
# Security #
############################
## Mail user / group
# Good practice: you should create a dedicated Linux user to send mails. That one is called "virtualMail"
virtual_uid_maps = static:5000
virtual_gid_maps = static:5000
## TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
Don't forget to adjust:
- Email global settings
- myhostname
- myorigin
- mydestination
- mynetworks
- Email accounts
- virtual_mailbox_base
- Security
- virtual_uid_maps
- virtual_gid_maps
Other
## Security libraries
# SASL is the Simple Authentication and Security Layer, a method for adding authentication support to connection-based protocols.
apt-get install libsasl2-modules libsasl2-modules-sql libgsasl7 libauthen-sasl-cyrus-perl sasl2-bin
# Authentication using MySQL
apt-get install libpam-mysql
## Anti-virus
apt-get install clamav-base libclamav6 clamav-daemon clamav-freshclam
## SPAM killer
apt-get install spamassassin spamc
## Interface to scan emails for virus & spam
apt-get install amavisd-new
## Utility to SEND emails
apt-get install postfix postfix-mysql
## Utility to RECEIVE emails
apt-get install courier-base courier-authdaemon courier-authlib-mysql courier-imap courier-imap-ssl courier-pop courier-pop-ssl courier-ssl