• CentOS-7
• Possible on one system, or on two separate systems (all connections between Postfix and Dovecot are over the network).
• One user-database (SASL serviced by Dovecot).
• virtual-users (no unix-users on the system for the users of the mailstore).
• Delivery from Postfix to Dovecot with LMTP over localhost or the public-ip with 24/tcp
• SASL username/pw lookups over localhost or the public-ip with 12345/tcp
• 2 mailboxes (2 mailadresses each).

Hostname: vps1.laboratory.local

Software:

yum install  postfix

Make x509 certs:

openssl req -utf8 -newkey rsa:2048 -keyout /etc/postfix/tls.key -nodes -x509 -days 3650 -out /etc/postfix/tls.crt -set_serial 0

Firewall ports:

firewall-cmd --add-port={25/tcp,587/tcp} --permanent
firewall-cmd --reload

In: /etc/postfix/master.cf

#
smtp      inet  n       -       n       -       -       smtpd
#
587       inet n       -       n       -       -       smtpd
   -o smtpd_enforce_tls=yes
   -o smtpd_sasl_auth_enable=yes
   -o syslog_name=postfix/submission
   -o smtpd_tls_security_level=encrypt
   -o smtpd_client_restrictions=permit_sasl_authenticated,reject
#
pickup    unix  n       -       n       60      1       pickup
cleanup   unix  n       -       n       -       0       cleanup
qmgr      unix  n       -       n       300     1       qmgr
tlsmgr    unix  -       -       n       1000?   1       tlsmgr
rewrite   unix  -       -       n       -       -       trivial-rewrite
bounce    unix  -       -       n       -       0       bounce
defer     unix  -       -       n       -       0       bounce
trace     unix  -       -       n       -       0       bounce
verify    unix  -       -       n       -       1       verify
flush     unix  n       -       n       1000?   0       flush
proxymap  unix  -       -       n       -       -       proxymap
proxywrite unix -       -       n       -       1       proxymap
smtp      unix  -       -       n       -       -       smtp
relay     unix  -       -       n       -       -       smtp
showq     unix  n       -       n       -       -       showq
error     unix  -       -       n       -       -       error
retry     unix  -       -       n       -       -       error
discard   unix  -       -       n       -       -       discard
local     unix  -       n       n       -       -       local
virtual   unix  -       n       n       -       -       virtual
lmtp      unix  -       -       n       -       -       lmtp
anvil     unix  -       -       n       -       1       anvil
scache    unix  -       -       n       -       1       scache

In: /etc/postfix/main.cf

data_directory = /var/lib/postfix
queue_directory = /var/spool/postfix
command_directory = /usr/sbin
daemon_directory = /usr/libexec/postfix
mail_owner = postfix
unknown_local_recipient_reject_code = 550
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
sendmail_path = /usr/sbin/sendmail.postfix
newaliases_path = /usr/bin/newaliases.postfix
mailq_path = /usr/bin/mailq.postfix
setgid_group = postdrop
html_directory = no

smtpd_tls_cert_file = /etc/postfix/tls.crt
smtpd_tls_key_file = /etc/postfix/tls.key
smtpd_use_tls = yes

smtpd_banner = postoffice.laboratory.local  ESMTP
disable_vrfy_command = yes
biff = no
append_dot_mydomain = no
myhostname = vps1.laboratory.local
myorigin = laboratory.local
mydestination = vps1.laboratory.local, localhost
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_command = procmail -a "$EXTENSION"
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = ipv4

virtual_alias_domains = /etc/postfix/virtual-domains

virtual_alias_maps = hash:/etc/postfix/virtual
transport_maps = hash:/etc/postfix/transport

smtpd_sasl_type = dovecot
smtpd_sasl_path = inet:vps2.laboratory.local:12345
smtpd_sasl_auth_enable = no
smtpd_sasl_security_options = noanonymous, noplaintext
smtpd_sasl_tls_security_options = noanonymous
smtpd_tls_auth_only = yes
smtpd_sasl_authenticated_header = yes

smtpd_recipient_restrictions =
   permit_mynetworks,
   permit_sasl_authenticated,
   reject_unauth_destination

In: /etc/postfix/virtual-domains

example.com
example2.com

In: /etc/postfix/virtual

# e-mail addr.:         username @ servername (of the Dovecot-server):

info@example.com       sv@vps2.laboratory.local
sv@example.com         sv@vps2.laboratory.local

info@example2.com      ln@vps2.laboratory.local
ln@example2.com        ln@vps2.laboratory.local

After editting:

postmap /etc/postfix/virtual

In: /etc/postfix/transport

sv@vps2.laboratory.local   lmtp:vps2.laboratory.local:24
ln@vps2.laboratory.local   lmtp:vps2.laboratory.local:24

After editting:

postmap /etc/postfix/transport

The SE-Linux configuration is out of the scope of this howto.

Hostname: vps2.laboratory.local

firewall:

firewall-cmd --add-port={24/tcp,143/tcp,993/tcp,4190/tcp,12345/tcp} --permanent
firewall-cmd --reload

Software:

yum install  dovecot

En voeg toe voor Sieve:

yum install dovecot-pigeonhole

Create directories and files:

mkdir /var/dovecot/
mkdir /var/dovecot/mail
mkdir /var/dovecot/sieve
mkdir /var/dovecot/conf
#
touch /var/dovecot/conf/users
#
chown -R dovecot:dovecot  /var/dovecot
touch /var/log/dovecot.log
chown dovecot:dovecot /var/log/dovecot.log

Make x509 certs:

openssl req -utf8 -newkey rsa:2048 -keyout /var/dovecot/conf/tls.key -nodes -x509 -days 3650 -out /var/dovecot/conf/tls.crt -set_serial 0

Create usernames and pw's (for the SASL-db):

The IMAP-users are created by adding a line in the users file. It has two columns, separated by a colon. The first column is the username, the second line contans the sha512-crypt which can be generated by executing:

doveadm pw -s SHA512-CRYPT

The result in /var/dovecot/conf/users will be like:

...
sv:{SHA512-CRYPT}$6$T5tUmkrjF2mAbo9G$3EEvR08UCHb11KCmCHbCaPcd1xv7CylpfdZgu3gv0WddRZGoF1drU62aHHEU9U4VTeTsM/wlxI2svBXsd7auX0
...
ln:{SHA512-CRYPT}$6$RHC1lIs0bS.ggVzR$NRaTNB.SJW7.sTcFbMcbfRZdJwEllNCM4zmROOxhiTBqQr4B4oxFnOAA1I.BknbKbSZ7uuvk5Z6k3JjT1Jonq/
...

In: /etc/dovecot/dovecot.conf

log_path = /var/log/dovecot.log

mail_location = maildir:/var/dovecot/data/%n/mail

auth_mechanisms = plain login
disable_plaintext_auth = no

#ssl_ca = </var/dovecot/conf/
ssl_cert = </var/dovecot/conf/tls.crt
ssl_key = </var/dovecot/conf/tls.key


# Default:
namespace inbox {
  inbox = yes
  location = 
     mailbox Drafts {
       special_use = \Drafts
     }
     mailbox Junk {
       special_use = \Junk
     }
     mailbox Sent {
       special_use = \Sent
     }
     #mailbox "Sent Messages" {
     #  special_use = \Sent
     #}
     mailbox Trash {
       special_use = \Trash
     }
  prefix = 
}

passdb {
  driver = passwd-file
  args = scheme=CRYPT username_format=%n /var/dovecot/conf/users
}

first_valid_uid = 2

userdb {
  # For static type, LDA verify the user's existence by lookup passdb
  #   ( http://wiki2.dovecot.org/UserDatabase/Static )
  driver = static
  args = uid=dovecot gid=dovecot home=/var/dovecot/data/%n/mail
}


protocols = "imap lmtp sieve"


protocol lmtp {
  mail_plugins = $mail_plugins sieve
}

service managesieve-login {
  inet_listener sieve {
    address = 0.0.0.0
    port = 4190
  }
  service_count = 1
  process_min_avail = 1
}

service managesieve {
}

#protocol managesieve {
#  disable_plaintext_auth = no
#}

protocol sieve {
}

plugin {
  sieve =      /var/dovecot/data/%n/managesieve/.dovecot.sieve
  sieve_dir =  /var/dovecot/data/%n/managesieve/sieve
}


# ###############################
service imap-login {
  inet_listener imap {
    port = 143
  }
  inet_listener imaps {
    port = 993
  }
}

protocol imap {
  disable_plaintext_auth = no
}


service lmtp {
  inet_listener lmtp {
    address = 0.0.0.0
    port = 24
  }
  user = dovecot
}


service auth-worker {
  # Forbid to access /etc/shadow
  user = $default_internal_user
}

service auth {
  inet_listener saslauth {
     address = 0.0.0.0
     port = 12345
  }
}

Enable and start the Dovecot:

systemctl start dovecot
systemctl enable dovecot

Make a connection with each mailbox with a MUA (mutt or Thunderbird) first before sending mail to the LMTP-connection. This will let Dovecot create the mailfolder structure for the mailbox to be stored. See: /var/dovecot/data/ (each username has it's own directory here).

Connect info for the MUA:

IMAP host:port = vps2.laboratory.local : 993
SMTP host:port = vps1.laboratory.local : 587
loginname = sv

Test with:

telnet  vps1.laboratory.local 25