The following article will show you how to install and run simple POP3/IMAP/SMTP mail server in your CentOS VPS using virtual users and domains with Postfix and Dovecot
What is Postfix? It is a drop in replacement for the old and mature Sendmail. Postfix also attempts to be very fast, easy to administer, and secure.
What is Dovecot? It is an open source IMAP and POP3 server for *NIX-like systems, written primarily with security in mind.
PRE-REQ
You may want to check if your hostname/domainname is a valid FQDN (fully qualified domain name) and it has a valid MX DNS record.
## if ! type -path “dig” > /dev/null 2>&1; then yum install bind-utils -y; fi
## DOMAIN=mydomain.com
## NSHOSTS=( “$(dig @4.2.2.2 +short MX ${DOMAIN}|sort -n|cut -d’ ‘ -f2)” )
## for NS in ${NSHOSTS[@]}; do printf “%-15s => %-s\n” “$(dig @4.2.2.2 +short A ${NS})” “${NS}”; done
## unset DOMAIN NSHOSTS
UPDATE THE SYSTEM
## screen -U -S mailserver-screen
## yum update
SET-UP SYSTEM USER
create group used for virtual mailboxes
## groupadd vmail -g 2222
create user used for virtual mailboxes
## useradd vmail -r -g 2222 -u 2222 -d /var/vmail -m -c “mail user”
INSTALL POSTFIX
## yum remove exim sendmail
## yum install postfix cronie
edit postfix main.cf configuration file
## cp /etc/postfix/main.cf{,.orig}
## vim /etc/postfix/main.cf
queue_directory = /var/spool/postfix
command_directory = /usr/sbin
daemon_directory = /usr/libexec/postfix
data_directory = /var/lib/postfix
mail_owner = postfix
unknown_local_recipient_reject_code = 550
alias_maps = hash:/etc/postfix/aliases
alias_database = $alias_maps
inet_interfaces = all
inet_protocols = ipv4
mydestination = $myhostname, localhost.$mydomain, localhost
debug_peer_level = 2
debugger_command =
PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin
ddd $daemon_directory/$process_name $process_id & sleep 5
sendmail_path = /usr/sbin/sendmail.postfix
newaliases_path = /usr/bin/newaliases.postfix
mailq_path = /usr/bin/mailq.postfix
setgid_group = postdrop
html_directory = no
manpage_directory = /usr/share/man
sample_directory = /usr/share/doc/postfix-2.6.6/samples
readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES
relay_domains = *
virtual_alias_maps=hash:/etc/postfix/vmail_aliases
virtual_mailbox_domains=hash:/etc/postfix/vmail_domains
virtual_mailbox_maps=hash:/etc/postfix/vmail_mailbox
virtual_mailbox_base = /var/vmail
virtual_minimum_uid = 2222
virtual_transport = virtual
virtual_uid_maps = static:2222
virtual_gid_maps = static:2222
smtpd_sasl_auth_enable = yes
smtpd_sasl_type = dovecot
smtpd_sasl_path = /var/run/dovecot/auth-client
smtpd_sasl_security_options = noanonymous
smtpd_sasl_tls_security_options = $smtpd_sasl_security_options
smtpd_sasl_local_domain = $mydomain
broken_sasl_auth_clients = yes
smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
create vmail_domains configuration file. this is where you add your virtual domains.
## vim /etc/postfix/vmail_domains
mydomain.com OK
my-otherdomain.com OK
create vmail_mailbox configuration file. this is where you define your mailboxes.
## vim /etc/postfix/vmail_mailbox
info@mydomain.com mydomain.com/info/
info@my-otherdomain.com my-otherdomain.com/info/
create vmail_aliases configuration file. this is where you define your virtual aliases.
## vim /etc/postfix/vmail_aliases
info@mydomain.com info@mydomain.com
info@my-otherdomain.com foo@bar.tld
hash the configuration files
## postmap /etc/postfix/vmail_domains
## postmap /etc/postfix/vmail_mailbox
## postmap /etc/postfix/vmail_aliases
## touch /etc/postfix/aliases
## vim +/submission /etc/postfix/master.cf
submission inet n – n – – smtpd
INSTALL DOVECOT
## yum install dovecot
edit dovecot dovecot.conf configuration file
## cp /etc/dovecot/dovecot.conf{,.orig}
## vim /etc/dovecot/dovecot.conf
listen = *
ssl = no
protocols = imap lmtp
disable_plaintext_auth = no
auth_mechanisms = plain login
mail_access_groups = vmail
default_login_user = vmail
first_valid_uid = 2222
first_valid_gid = 2222
#mail_location = maildir:~/Maildir
mail_location = maildir:/var/vmail/%d/%n
passdb {
driver = passwd-file
args = scheme=SHA1 /etc/dovecot/passwd
}
userdb {
driver = static
args = uid=2222 gid=2222 home=/var/vmail/%d/%n allow_all_users=yes
}
service auth {
unix_listener auth-client {
group = postfix
mode = 0660
user = postfix
}
user = root
}
service imap-login {
process_min_avail = 1
user = vmail
}
create virtual user’s configuration file passwd. this is where usernames and password hashes will be stored.
## touch /etc/dovecot/passwd
## doveadm pw -s sha1 | cut -d ‘}’ -f2
## vim /etc/dovecot/passwd
info@mydomain.com:DOzcsKI8HY0bg8LAuz0DPKwS3WA=
## chown root: /etc/dovecot/passwd
## chmod 600 /etc/dovecot/passwd
START SERVICES
## chkconfig postfix on
## chkconfig dovecot on
## service postfix restart
## service dovecot restart
TEST THE SET-UP
Open your favorite e-mail client and configure it to use the newly created info@mydomain.com account. Try to send/receive an email. If you experience any issues, check if there’s something logged in /var/log/maillog
you can also use swaks to test your smtp server, for example:
swaks –to support@mydomain.com –from email@address.net
more information about swaks you can find at man swaks
ADD ANOTHER ACCOUNT
set-up account’s mailbox
## vim /etc/postfix/vmail_mailbox
…
support@mydomain.com mydomain.com/support/
set-up account’s alias(es)
## vim /etc/postfix/vmail_aliases
…
support@mydomain.com support@mydomain.com
postmap configuration files and restart postfix
## postmap /etc/postfix/vmail_mailbox
## postmap /etc/postfix/vmail_aliases
## service postfix restart
generate password hash and add username:password-hash to passwd file.
## doveadm pw -s sha1 | cut -d ‘}’ -f2
## vim /etc/dovecot/passwd
…
support@mydomain.com:DOzcsKI8HY0bg8LAuz0DPKwS3WA=