[Dovecot] Unable to get Dovecot LDA/deliver working

[Frank van Amsterdam]

I want to setup Dovecot LDA, but I don't understand what I'm doing anymore. 
I have to note that I'm a Linux beginner. I've been trying now for several 
months and I'm about to give up. Till so far I'm having no result. :-(

My current setup is done as described at http://www.linuxmail.info. We use 
Postfix 2.3.3 (with Postgrey, Spamassassin and ClamAV), Dovecot 1.2.11 and 
OpenLDAP 2.4.1 on CentOS 5.5. All incoming e-mail are delivered by Postfix 
in the users' maildir. We use this as a base for SOGo, our groupware 
solution and it runs smoothly.

I have to setup a new mailserver, because we're standardising on Debian. My 
employer wants to have new functions like out-of-office-replies and 
forwarding. I want to make use of sieve. Unfortunately I don't know anyone 
who can help me.

My problem is that I don't understand how the delivery process is working. 
I've read much documentation from Postfix and Dovecot, but I find it too 
difficult to understand.

What do I understand? I know that I have to make changes in /etc/dovecot, 
/etc/postfix/main.cf and /etc/postfix/master.cf as described at 
http://wiki.dovecot.org/LDA.

/etc/dovecot.conf

# OS: Linux 2.6.18-028stab064.7 i686 CentOS release 5.5 (Final) reiserfs
base_dir: /var/run/dovecot/
protocols: imap imaps pop3 pop3s managesieve
ssl: no
version_ignore: yes
login_dir: /var/run/dovecot/login
login_executable(default): /usr/local/libexec/dovecot/imap-login
login_executable(imap): /usr/local/libexec/dovecot/imap-login
login_executable(pop3): /usr/local/libexec/dovecot/pop3-login
login_executable(managesieve): /usr/libexec/dovecot/managesieve-login
mail_location: maildir:/home/vmail/%u/Maildir
mail_executable(default): /usr/local/libexec/dovecot/imap
mail_executable(imap): /usr/local/libexec/dovecot/imap
mail_executable(pop3): /usr/local/libexec/dovecot/pop3
mail_executable(managesieve): /usr/libexec/dovecot/managesieve
mail_plugin_dir(default): /usr/local/lib/dovecot/imap
mail_plugin_dir(imap): /usr/local/lib/dovecot/imap
mail_plugin_dir(pop3): /usr/local/lib/dovecot/pop3
mail_plugin_dir(managesieve): /usr/local/lib/dovecot/managesieve
imap_client_workarounds(default): delay-newmail outlook-idle netscape-eoh
imap_client_workarounds(imap): delay-newmail outlook-idle netscape-eoh
imap_client_workarounds(pop3):
imap_client_workarounds(managesieve):
pop3_client_workarounds(default):
pop3_client_workarounds(imap):
pop3_client_workarounds(pop3): outlook-no-nuls oe-ns-eoh
pop3_client_workarounds(managesieve):
managesieve_logout_format(default): bytes=%i/%o
managesieve_logout_format(imap): bytes=%i/%o
managesieve_logout_format(pop3): bytes=%i/%o
managesieve_logout_format(managesieve): bytes ( in=%i : out=%o )
lda:
  postmaster_address: postmaster at domain.nl
  mail_plugins: cmusieve
  mail_plugin_dir: /usr/lib/dovecot/lda
  deliver_log_format: msgid=%m: %$ -- FROM=%f SUBJECT=%s
  log_path: /var/log/dovecot-deliver.log
  info_log_path: /var/log/dovecot-deliver.log
  syslog_facility: mail
  sendmail_path: /usr/lib/sendmail
  rejection_subject: Rejected: %s
  rejection_reason: Your message to <%t> was automatically rejected:%n%r
  auth_socket_path: /usr/local/var/run/dovecot-auth-master
auth default:
  mechanisms: plain login
  username_format: %Lu
  passdb:
    driver: ldap
    args: /etc/dovecot-ldap.conf
  userdb:
    driver: static
    args: uid=500 gid=500 home=/home/vmail/%u
  socket:
    type: listen
    client:
      path: /var/spool/postfix/private/auth
      mode: 432
      user: postfix
      group: postfix
    master:
      path: /var/run/dovecot/auth-master
      mode: 384
      user: vmail
      group: vmail
plugin:
  sieve: /var/sieve-scripts/%u.sieve
  sieve_dir: %h/sieve
  sieve_global_dir: /var/lib/dovecot/sieve/global/

/etc/postfix/main.cf

virtual_mailbox_domains = /etc/postfix/domains ## Plain text file with the 
domains
virtual_mailbox_base = /home/vmail
virtual_mailbox_maps = ldap:/etc/postfix/ldap-users.cf
virtual_alias_maps = ldap:/etc/postfix/ldap-groups.cf
virtual_uid_maps = static:500
virtual_gid_maps = static:500
dovecot_destination_recipient_limit = 1
#virtual_transport = dovecot ## Commented out to deliver by Postfix

/etc/postfix/ldap-users.cf

server_host = localhost
search_base = dc=domain,dc=com
version = 3
query_filter = (&(objectclass=mailUser)(mail=%s))
result_attribute = uid
result_format = %s/Maildir/

/etc/postfix/ldap-groups.cf

server_host = localhost
search_base = dc=domain,dc=com
version = 3
query_filter = (&(objectclass=mailGroup)(mail=%s))
leaf_result_attribute = mail
special_result_attribute = member

/etc/postfix/master.cf

dovecot   unix  -       n       n       -       -       pipe
 flags=DRhu user=vmail:vmail argv=/usr/local/libexec/dovecot/deliver -d 
<username>

I hope someone can help me, because many people on the internet say that it 
is easy. If anyone needs more information or anyone can help me, please 
contact me.

Best, Frank

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LS: I know that I'm using Hotmail, but I want to post this anonymously.