Step 4: Install and configure dovecot

apt-get install dovecot-imapd dovecot-pop3d

This will install dovecot and all necessary files and also create the standard ssl certificates for IMAPs and POP3s.

Now we back up the original configuration file for safe keeping.

mv /etc/dovecot/dovecot.conf /etc/dovecot/dovecot.conf.bck
mv /etc/dovecot/dovecot-ldap.conf /etc/dovecot/dovecot-ldap.conf.bck

Next you can create new configuration files with the examples provide below.

vi /etc/dovecot/dovecot.conf

auth_verbose = yes
mail_debug = yes

base_dir = /var/run/dovecot/
protocols = imap imaps pop3 pop3s
protocol lda {
  postmaster_address = postmaster@example.tld
  auth_socket_path = /var/run/dovecot/auth-master
  log_path = /var/log/dovecot-deliver.log
  info_log_path = /var/log/dovecot-deliver.log
  }
listen = *
shutdown_clients = yes
log_path = /var/log/dovecot.log
info_log_path = /var/log/mail.log
log_timestamp = "%b %d %H:%M:%S "
syslog_facility = mail
disable_plaintext_auth = no
ssl_disable = no
ssl_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
ssl_key_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
login_chroot = yes
login_user = postfix
login_process_per_connection = yes
login_processes_count = 2
login_max_processes_count = 128
login_max_connections = 256
login_greeting = Welkom bij Webhabitat's Dovecot eMail Server.
login_log_format_elements = user=<%u> method=%m rip=%r lip=%l %c
login_log_format = %$: %s
default_mail_env = maildir:/home/vmail/domains/%d/%u
first_valid_uid = 108 # REMEBER THIS MUST BE CHANGED TO YOUR UID FOR "postfix" FROM /etc/passwd
pop3_uidl_format = %08Xu%08Xv
auth default {
    mechanisms = PLAIN LOGIN
    passdb ldap {
        args = /etc/dovecot/dovecot-ldap.conf
    }
    userdb ldap {
        args = /etc/dovecot/dovecot-ldap.conf
    }
socket listen {
                master {
                        path = /var/run/dovecot/auth-master
                                mode = 0600
                        user = vmail
                        group = vmail
                }
                client {
                        path = /var/spool/postfix/private/auth
                        mode = 0660
                        user = postfix
                        group = postfix
                }
        }
        user = vmail
}

vi /etc/dovecot/dovecot-ldap.conf

hosts = localhost
auth_bind = yes
auth_bind_userdn = mail=%u,vd=%d,o=hosting,dc=example,dc=tld
ldap_version = 3
base = dc=example,dc=tld
dn = cn=admin,dc=example,dc=tld
dnpass = secret
deref = never
scope = subtree
user_filter = (&(objectClass=VirtualMailAccount)(accountActive=TRUE)(mail=%u))
pass_filter = (&(objectClass=VirtualMailAccount)(accountActive=TRUE)(mail=%u))
default_pass_scheme = MD5
# the uid of your vmail user
user_global_uid = 1000
# the guid of your vmail group
user_global_gid = 1000

Note: Remember to change example.tld to your own domain.tld see assumptions.

The follwoing entry in dovecot.conf enables sasl:

socket listen {
                master {
                        path = /var/run/dovecot/auth-master
                                mode = 0600
                        user = vmail
                        group = vmail
                }
                client {
                        path = /var/spool/postfix/private/auth
                        mode = 0660
                        user = postfix
                        group = postfix
                }
        }
        user = vmail
}

The following entry in dovecot.conf provides session and logging for dovecot deliver:

protocol lda {
  postmaster_address = postmaster@example.tld
  auth_socket_path = /var/run/dovecot/auth-master
  log_path = /var/log/dovecot-deliver.log
  info_log_path = /var/log/dovecot-deliver.log
  }

At this moment I haven't gotten dovecot to use the quota entries provided by phamm, this will be an addon in the (very, hopefully :) ) future.

This concludes the dovecot configuration.