Oracle Linux/Simple IMAP Server

Overview

Dovecot for POP/IMAP
Postfix for SMTP

Setup SSL

Just going to use a simple self-signed cert. However, before we can, we need to create a symlink so that we utilize the existing private directory and create a link from the standard location for private keys to the actual location.

~$ cd /etc/ssl/
~$ sudo ln -s ../pki/tls/private/ private
~$ sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/ssl/private/mail.key -out /etc/ssl/certs/mailcert.pem

Postfix

Make sure exim4 is not installed and verify that postfix is installed and at the latest version

~$ sudo rpm -qa | grep exim
~$ sudo yum install postfix

Edit the following: /etc/postfix/master.cf

uncomment:
submission inet n       -       n       -       -       smtpd
  -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
add:
  -o syslog_name=postfix/submission
  -o smtpd_tls_wrappermode=no
  -o smtpd_recipient_restrictions=permit_mynetworks,permit_sasl_authenticated,reject
  -o smtpd_sasl_type=dovecot
  -o smtpd_sasl_path=private/auth

Let's back up the next file we'll be modifying:

~$ sudo cp /etc/postfix/main.cf /etc/postfix/main.cf.original

Edit the following: /etc/postfix.main.cf

uncomment and edit:
  myhostname = mail.domain.com
  myorigin = /etc/mailname
  inet_interfaces = all
  mydestination = mail.domain.com, domain.com, localhost, localhost,localdomain
  mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
  relayhost =  

uncomment:
  recipient_delimiter = +
  local_recipient_maps = proxy:unix:passwd.byname $alias_maps

comment out:
  inet_interfaces = localhost

add:
  # Adding mailbox size limit of 0 to remove restrictions on size
  mailbox_size_limit = 0

  # Adding SSL
  smtpd_tls_cert_file=/etc/ssl/certs/mailcert.pem
  smtpd_tls_key_file=/etc/ssl/private/mail.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
  smtpd_tls_security_level=may
  smtpd_tls_protocols = !SSLv2, !SSLv3

verify:
  alias_maps = hash:/etc/aliases
  alias_database = hash:/etc/aliases

Dovecot

~$ sudo yum install dovecot.x86_64

Backup /etc/dovecot/dovecot.conf

~$ sudo cp /etc/dovecot/dovecot.conf /etc/dovecot/dovecot.conf.original

Remove the old dovecot.conf file and create a new one

~$ sudo rm /etc/dovecot/dovecot.conf
~$ sudo vi /etc/dovecot/dovecot.conf

You'll want to add the following to your new dovecot.conf file:

log_timestamp = "%Y-%m-%d %H:%M:%S "
disable_plaintext_auth = no
mail_privileged_group = mail
mail_location = mbox:~/mail:INBOX=/var/mail/%u
userdb {
  driver = passwd
}
passdb {
  args = %s
  driver = pam
}
protocols = "imap pop3"

service auth {
  unix_listener /var/spool/postfix/private/auth {
    group = postfix
    mode = 0660
    user = postfix
  }
}

ssl=required
ssl_cert = </etc/ssl/certs/mailcert.pem
ssl_key = </etc/ssl/private/mail.key

Lastly, make a couple of symlinks so authentication via pop/imap works.

~$ sudo ln -s /etc/pam.d/dovecot /etc/pam.d/imap
~$ sudo ln -s /etc/pam.d/dovecot /etc/pam.d/pop3

Wrap Up

~$ sudo newaliases
~$ sudo postfix stop
~$ sudo postfix start
~$ sudo dovecot restart

Also, with every new user that you create, you'll need to do the following:

~$ sudo chmod -R 777 /var/spool/mail

Without doing this, the users wont have access to create new folders or an Inbox and possibly messages.