dovecot - Sep 2005 - Moving messages takes a longgggggg..... time. (Timeouts?) dovecot.conf help?

Hi,

I'm trying to get dovecot set up better.  I am using 1.0alpha3.  It 
takes a long long time to move messages for some reason.   It seems it 
may be a timeout  thing, because neither the client or server is using 
any cpu time or disk i/o or network to speak of.  (To move maybe 400 
messages, it seems to take maybe half an hour, maybe longer.)  With 
alpha 2 I was getting messages from Thunderbird saying that the server 
was unable to move messages, would I like to continue.  I haven't seen 
any of these lately, but when I updated to alpha3 I also made some 
dovecot.conf changes.  I'm running this on OS X with a 450 MHz cube with 
1.2 Gig of ram and a 7200 RPM hard drive.

I have a lot of rules that move messages to various mailboxes and I get 
a lot of mail, so this is important to me.  I have a very large Maildir 
set of mailboxes (about 40 of them with up to 70,000 messages in each 
mailbox).  I have finally got it so that it will load the mailbox 
headers pretty quickly in Thunderbird.  It takes about 15 to 30 seconds 
to load a message, but that is acceptable to me.

Here is my dovecot.conf.  Can anyone give me some tips?

## Dovecot 1.0 configuration file

# '#' character and everything after it is treated as comments. Extra
spaces
# and tabs are ignored. If you want to use either of these explicitly, 
put the
# value inside quotes, eg.: key = "# char and trailing whitespace  "

# Default values are shown after each value, it's not required to uncomment
# any of the lines. Exception to this are paths, they're just examples
# with real defaults being based on configure options. The paths listed here
# are for configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var
# --with-ssldir=/etc/ssl

# Base directory where to store runtime data.
base_dir = /var/run/dovecot/

# Protocols we want to be serving:
#  imap imaps pop3 pop3s
#protocols = imap imaps

# IP or host address where to listen in for connections. It's not currently
# possible to specify multiple addresses. "*" listens in all IPv4 
interfaces.
# "[::]" listens in all IPv6 interfaces, but may also listen in all
IPv4
# interfaces depending on the operating system.  If you want to specify 
ports
# for each service, you will need to configure these settings inside the
# protocol imap/pop3 { ... } section, so you can specify different ports
# for IMAP/POP3.
#listen = *

# IP or host address where to listen in for SSL connections. Defaults
# to above if not specified.
#ssl_listen 
# Disable SSL/TLS support.
ssl_disable = yes

# PEM encoded X.509 SSL/TLS certificate and private key. They're opened 
before
# dropping root privileges, so keep the key file unreadable by anyone but
# root. Included doc/mkcert.sh can be used to easily generate self-signed
# certificate, just make sure to update the domains in dovecot-openssl.cnf
#ssl_cert_file = /etc/ssl/certs/dovecot.pem
#ssl_key_file = /etc/ssl/private/dovecot.pem

# File containing trusted SSL certificate authorities. Usually not needed.
#ssl_ca_file 
# Request client to send a certificate.
#ssl_verify_client_cert = no

# SSL parameter file. Master process generates this file for login 
processes.
# It contains Diffie Hellman and RSA parameters.
#ssl_parameters_file = /var/run/dovecot/ssl-parameters.dat

# How often to regenerate the SSL parameters file. Generation is quite CPU
# intensive operation. The value is in hours, 0 disables regeneration
# entirely.
#ssl_parameters_regenerate = 24

# SSL ciphers to use
#ssl_cipher_list = ALL:!LOW

# Disable LOGIN command and all other plaintext authentications unless
# SSL/TLS is used (LOGINDISABLED capability). Note that 127.*.*.* and
# IPv6 ::1 addresses are considered secure, this setting has no effect if
# you connect from those addresses.
disable_plaintext_auth = no

# Use this logfile instead of syslog(). /dev/stderr can be used if you 
want to
# use stderr for logging (ONLY /dev/stderr - otherwise it is closed).
#log_path 
# For informational messages, use this logfile instead of the default
#info_log_path 
# Prefix for each line written to log file. % codes are in strftime(3)
# format.
#log_timestamp = "%b %d %H:%M:%S "

##
## Login processes
##

# Directory where authentication process places authentication UNIX sockets
# which login needs to be able to connect to. The sockets are created when
# running as root, so you don't have to worry about permissions. Note that
# everything in this directory is deleted when Dovecot is started.
#login_dir = /var/run/dovecot/login

# chroot login process to the login_dir. Only reason not to do this is 
if you
# wish to run the whole Dovecot without roots.
# http://wiki.dovecot.org/Rootless
#login_chroot = yes

# User to use for the login process. Create a completely new user for this,
# and don't use it anywhere else. The user must also belong to a group where
# only it has access, it's used to control access for authentication 
process.
# Note that this user is NOT used to access mails.
# http://wiki.dovecot.org/UserIds
#login_user = dovecot

# Set max. process size in megabytes. If you don't use
# login_process_per_connection you might need to grow this.
login_process_size = 4096

# Should each login be processed in it's own process (yes), or should one
# login process be allowed to process multiple connections (no)? Yes is more
# secure, espcially with SSL/TLS enabled. No is faster since there's no need
# to create processes all the time.
login_process_per_connection = no

# Number of login processes to create. If login_process_per_user is
# yes, this is the number of extra processes waiting for users to log in.
#login_processes_count = 3

# Maximum number of extra login processes to create. The extra process count
# usually stays at login_processes_count, but when multiple users start 
logging
# in at the same time more extra processes are created. To prevent 
fork-bombing
# we check only once in a second if new processes should be created - if all
# of them are used at the time, we double their amount until limit set 
by this
# setting is reached. This setting is used only if login_process_per_use 
is yes.
#login_max_processes_count = 128

# Maximum number of connections allowed in login state. When this limit is
# reached, the oldest connections are dropped. If login_process_per_user
# is no, this is a per-process value, so the absolute maximum number of 
users
# logging in actually login_processes_count * max_logging_users.
#login_max_logging_users = 256

# Greeting message for clients.
#login_greeting = Dovecot ready.

# Space-separated list of elements we want to log. The elements which have
# a non-empty variable value are joined together to form a comma-separated
# string.
#login_log_format_elements = user=<%u> method=%m rip=%r lip=%l %c

# Login log format. %$ contains login_log_format_elements string, %s 
contains
# the data we want to log.
#login_log_format = %$: %s

##
## Mail processes
##

# Maximum number of running mail processes. When this limit is reached,
# new users aren't allowed to log in.
#max_mail_processes = 1024
max_mail_processes = 4096

# Show more verbose process titles (in ps). Currently shows user name and
# IP address. Useful for seeing who are actually using the IMAP processes
# (eg. shared mailboxes or if same uid is used for multiple accounts).
#verbose_proctitle = no
verbose_proctitle = yes

# Show protocol level SSL errors.
#verbose_ssl = no
verbose_ssl = yes

# Valid UID range for users, defaults to 500 and above. This is mostly
# to make sure that users can't log in as daemons or other system users.
# Note that denying root logins is hardcoded to dovecot binary and can't
# be done even if first_valid_uid is set to 0.
#first_valid_uid = 500
#last_valid_uid = 0

# Valid GID range for users, defaults to non-root/wheel. Users having
# non-valid GID as primary group ID aren't allowed to log in. If user
# belongs to supplementary groups with non-valid GIDs, those groups are
# not set.
#first_valid_gid = 1
#last_valid_gid = 0

# Grant access to these extra groups for mail processes. Typical use 
would be
# to give "mail" group write access to /var/mail to be able to create 
dotlocks.
#mail_extra_groups mail_extra_groups = mail

# ':' separated list of directories under which chrooting is allowed for
mail
# processes (ie. /var/mail will allow chrooting to /var/mail/foo/bar too).
# This setting doesn't affect login_chroot or auth_chroot variables.
# WARNING: Never add directories here which local users can modify, that
# may lead to root exploit. Usually this should be done only if you don't
# allow shell access for users. See doc/configuration.txt for more 
information.
#valid_chroot_dirs 
# Default chroot directory for mail processes. This can be overridden for
# specific users in user database by giving /./ in user's home directory
# (eg. /home/./user chroots into /home). Note that usually there is no real
# need to do chrooting, Dovecot doesn't allow users to access files outside
# their mail directory anyway.
#mail_chroot 
# Enable mail process debugging. This can help you figure out why Dovecot
# isn't finding your mails.
#mail_debug = no
mail_debug=yes

# Default MAIL environment to use when it's not set. By leaving this empty
# dovecot tries to do some automatic detection as described in
# doc/mail-storages.txt. There's a few special variables you can use, eg.:
#
#   %u - username
#   %n - user part in user at domain, same as %u if there's no domain
#   %d - domain part in user at domain, empty if there's no domain
#   %h - home directory
#
# See doc/variables.txt for full list. Some examples:
#
#   default_mail_env = maildir:/var/mail/%1u/%u/Maildir
#   default_mail_env = mbox:~/mail/:INBOX=/var/mail/%u
#   default_mail_env = mbox:/var/mail/%d/%n/:INDEX=/var/indexes/%d/%n
#
#default_mail_env = mbox:~/Library/Mail/Mailboxes:INBOX=/var/mail/%u
default_mail_env = maildir:%h/Maildir

# If you need to set multiple mailbox locations or want to change default
# namespace settings, you can do it by defining namespace sections:
#
# You can have private, shared and public namespaces. The only difference
# between them is how Dovecot announces them to client via NAMESPACE
# extension. Shared namespaces are meant for user-owned mailboxes which are
# shared to other users, while public namespaces are for more globally
# accessible mailboxes.
#
# REMEMBER: If you add any namespaces, the default namespace must be added
# explicitly, ie. default_mail_env does nothing unless you have a namespace
# without a location setting. Default namespace is simply done by having a
# namespace with empty prefix.
#namespace private {
   # Hierarchy separator to use. You should use the same separator for all
   # namespaces or some clients get confused. '/' is usually a good one.
   #separator = /

   # Prefix required to access this namespace. This needs to be 
different for
   # all namespaces. For example "Public/".
   #prefix 
   # Physical location of the mailbox. This is in same format as
   # default_mail_env, which is also the default for it.
   #location 
   # There can be only one INBOX, and this setting defines which namespace
   # has it.
   #inbox = yes

   # If namespace is hidden, it's not advertised to clients via NAMESPACE
   # extension or shown in LIST replies. This is mostly useful when 
converting
   # from another server with different namespaces which you want to 
depricate
   # but still keep working. For example you can create hidden 
namespaces with
   # prefixes "~/mail/", "~%u/mail/" and "mail/".
   #hidden = yes
#}

# Space-separated list of fields to initially save into cache file. 
Currently
# these fields are allowed:
#
#  flags, date.sent, date.received, size.virtual, size.physical
#  mime.parts, imap.body, imap.bodystructure
#
# Different IMAP clients work in different ways, so they benefit from
# different cached fields. Some do not benefit from them at all. Caching 
more
# than necessary generates useless disk I/O, so you don't want to do that
# either.
#
# Dovecot attempts to automatically figure out what client wants and it 
keeps
# only that. However the first few times a mailbox is opened, Dovecot hasn't
# yet figured out what client needs, so it may not perform optimally. If you
# know what fields the majority of your clients need, it may be useful 
to set
# these fields by hand. If client doesn't actually use them, Dovecot will
# eventually drop them.
#
# Usually you should just leave this field alone. The potential benefits are
# typically unnoticeable.
#mail_cache_fields 
# Space-separated list of fields that Dovecot should never save to cache 
file.
# Useful if you want to save disk space at the cost of more I/O when the 
fields
# needed.
#mail_never_cache_fields 
# Like mailbox_check_interval, but used for IDLE command.
#mailbox_idle_check_interval = 30
mailbox_idle_check_interval = 15

# Allow full filesystem access to clients. There's no access checks 
other than
# what the operating system does for the active UID/GID. It works with both
# maildir and mboxes, allowing you to prefix mailboxes names with eg. /path/
# or ~user/.
#mail_full_filesystem_access = no

# Maximum allowed length for mail keyword name. It's only forced when trying
# to create new keywords.
#mail_max_keyword_length = 50
mail_max_keyword_length = 250

# Save mails with CR+LF instead of plain LF. This makes sending those mails
# take less CPU, especially with sendfile() syscall with Linux and FreeBSD.
# But it also creates a bit more disk I/O which may just make it slower.
#mail_save_crlf = no

# Use mmap() instead of read() to read mail files. read() seems to be a bit
# faster with my Linux/x86 and it's better with NFS, so that's the
default.
# Note that OpenBSD 3.3 and older don't work right with mail_read_mmaped 
= yes.
#mail_read_mmaped = no

# Don't use mmap() at all. This is required if you store indexes in remote
# filesystems (NFS or clustered filesystem).
#mmap_disable = no

# Don't write() to mmaped files. This is required for some operating systems
# which use separate caches for them, such as OpenBSD.
#mmap_no_write = no

# Locking method for index files. Alternatives are fcntl, flock and dotlock.
# Dotlocking uses some tricks which may create more disk I/O than other 
locking
# methods.
#lock_method = fcntl

# By default LIST command returns all entries in maildir beginning with dot.
# Enabling this option makes Dovecot return only entries which are 
directories.
# This is done by stat()ing each entry, so it causes more disk I/O.
# (For systems setting struct dirent->d_type, this check is free and it's
# done always regardless of this setting)
#maildir_stat_dirs = no

# Copy mail to another folders using hard links. This is much faster than
# actually copying the file. This is problematic only if something modifies
# the mail in one folder but doesn't want it modified in the others. I
don't
# know any MUA which would modify mail files directly. IMAP protocol also
# requires that the mails don't change, so it would be problematic in 
any case.
# If you care about performance, enable it.
#maildir_copy_with_hardlinks = no
maildir_copy_with_hardlinks = yes

# Which locking methods to use for locking mbox. There's four available:
#  dotlock: Create <mailbox>.lock file. This is the oldest and most
NFS-safe
#           solution. If you want to use /var/mail/ like directory, the 
users
#           will need write access to that directory.
#  fcntl  : Use this if possible. Works with NFS too if lockd is used.
#  flock  : May not exist in all systems. Doesn't work with NFS.
#  lockf  : May not exist in all systems. Doesn't work with NFS.
#
# You can use multiple locking methods; if you do the order they're declared
# in is important to avoid deadlocks if other MTAs/MUAs are using multiple
# locking methods as well. Some operating systems don't allow using some of
# them simultaneously.
#mbox_read_locks = fcntl
#mbox_write_locks = dotlock fcntl

# Maximum time in seconds to wait for lock (all of them) before aborting.
#mbox_lock_timeout = 300

# If dotlock exists but the mailbox isn't modified in any way, override the
# lock file after this many seconds.
#mbox_dotlock_change_timeout = 30

# When mbox changes unexpectedly we have to fully read it to find out what
# changed. If the mbox is large this can take a long time. Since the change
# is usually just a newly appended mail, it'd be faster to simply read the
# new mails. If this setting is enabled, Dovecot does this but still safely
# fallbacks to re-reading the whole mbox file whenever something in mbox 
isn't
# how it's expected to be. The only real downside to this setting is that if
# some other MUA changes message flags, Dovecot doesn't notice it 
immediately.
# Note that a full sync is done with SELECT, EXAMINE, EXPUNGE and CHECK
# commands.
#mbox_dirty_syncs = yes

# Like mbox_dirty_syncs, but don't do full syncs even with SELECT, EXAMINE,
# EXPUNGE or CHECK commands. If this is set, mbox_dirty_syncs is ignored.
#mbox_very_dirty_syncs = no

# Delay writing mbox headers until doing a full write sync (EXPUNGE and 
CHECK
# commands and when closing the mailbox). This is especially useful for POP3
# where clients often delete all mails. The downside is that our changes
# aren't immediately visible to other MUAs.
#mbox_lazy_writes = yes

# umask to use for mail files and directories
#umask = 0077

# Drop all privileges before exec()ing the mail process. This is mostly
# meant for debugging, otherwise you don't get core dumps. It could be a 
small
# security risk if you use single UID for multiple users, as the users could
# ptrace() each others processes then.
#mail_drop_priv_before_exec = no

# Set max. process size in megabytes. Most of the memory goes to mmap()ing
# files, so it shouldn't harm much even if this limit is set pretty high.
#mail_process_size = 256
mail_process_size = 4096

# Log prefix for mail processes. See doc/variables.txt for list of possible
# variables you can use.
#mail_log_prefix = "%Us(%u): "

##
## IMAP specific settings
##

protocol imap {
  # Login executable location.
  #login_executable = /usr/libexec/dovecot/imap-login

  # IMAP executable location
  #mail_executable = /usr/libexec/dovecot/imap
  # This would write rawlogs into ~/dovecot.rawlog/ directory:
  #mail_executable = /usr/libexec/dovecot/rawlog /usr/libexec/dovecot/imap

  # Maximum IMAP command line length in bytes. Some clients generate 
very long
  # command lines with huge mailboxes, so you may need to raise this if 
you get
  # "Too long argument" or "IMAP command line too large"
errors often.
  #imap_max_line_length = 65536
  imap_max_line_length = 262144

  # Support for dynamically loadable modules.
  #mail_use_modules = no
  #mail_modules = /usr/lib/dovecot/imap

  # Send IMAP capabilities in greeting message. This makes it 
unnecessary for
  # clients to request it with CAPABILITY command, so it saves one 
round-trip.
  # Many clients however don't understand it and ask the CAPABILITY anyway.
  #login_greeting_capability = no

  # Workarounds for various client bugs:
  #   delay-newmail:
  #     Send EXISTS/RECENT new mail notifications only when replying to NOOP
  #     and CHECK commands. Some clients ignore them otherwise, for example
  #     OSX Mail. Outlook Express breaks more badly though, without this it
  #     may show user "Message no longer in server" errors. Note that 
OE6 still
  #     breaks even with this workaround if synchronization is set to
  #     "Headers Only".
  #   outlook-idle:
  #     Outlook and Outlook Express never abort IDLE command, so if no mail
  #     arrives in half a hour, Dovecot closes the connection. This is still
  #     fine, except Outlook doesn't connect back so you don't see if 
new mail
  #     arrives.
  #   netscape-eoh:
  #     Netscape 4.x breaks if message headers don't end with the empty 
"end of
  #     headers" line. Normally all messages have this, but setting this
  #     workaround makes sure that Netscape never breaks by adding the 
line if
  #     it doesn't exist. This is done only for FETCH BODY[HEADER.FIELDS..]
  #     commands. Note that RFC says this shouldn't be done.
  #   tb-extra-mailbox-sep:
  #     With mbox storage a mailbox can contain either mails or 
submailboxes,
  #     but not both. Thunderbird separates these two by forcing server to
  #     accept '/' suffix in mailbox names in subscriptions list.
  #imap_client_workarounds = outlook-idle
  imap_client_workarounds = delay-newmail outlook-idle netscape-eoh 
tb-extra-mailbox-sep
}
 
##
## POP3 specific settings
##

protocol pop3 {
  # Login executable location.
  #login_executable = /usr/libexec/dovecot/pop3-login

  # POP3 executable location
  #mail_executable = /usr/libexec/dovecot/pop3

  # Don't try to set mails non-recent or seen with POP3 sessions. This is
  # mostly intended to reduce disk I/O. With maildir it doesn't move files
  # from new/ to cur/, with mbox it doesn't write Status-header.
  #pop3_no_flag_updates = no

  # Support LAST command which exists in old POP3 specs, but has been 
removed
  # from new ones. Some clients still wish to use this though. Enabling this
  # makes RSET command clear all \Seen flags from messages.
  #pop3_enable_last = no
 
  # POP3 UIDL format to use. You can use following variables:
  #
  #  %v - Mailbox UIDVALIDITY
  #  %u - Mail UID
  #  %m - MD5 sum of the mailbox headers in hex (mbox only)
  #  %f - filename (maildir only)
  #
  # If you want UIDL compatibility with other POP3 servers, use:
  #  UW's ipop3d         : %08Xv%08Xu
  #  Courier version 0   : %f
  #  Courier version 1   : %u
  #  Courier version 2   : %v-%u
  #  Cyrus (<= 2.1.3)    : %u
  #  Cyrus (>= 2.1.4)    : %v.%u
  #
  # Note that Outlook 2003 seems to have problems with %v.%u format which is
  # Dovecot's default, so if you're building a new server it would be a
good
  # idea to change this. %08Xu%08Xv should be pretty fail-safe.
  #pop3_uidl_format = %v.%u

  # POP3 logout format string:
  #  %t - number of TOP commands
  #  %T - number of bytes sent to client as a result of TOP command
  #  %r - number of RETR commands
  #  %R - number of bytes sent to client as a result of RETR command
  #  %d - number of deleted messages
  #  %m - number of messages (before deletion)
  #  %s - mailbox size in bytes (before deletion)
  #pop3_logout_format = top=%t/%T, retr=%r/%R, del=%d/%m, size=%s

  # Support for dynamically loadable modules.
  #mail_use_modules = no
  #mail_modules = /usr/lib/dovecot/pop3

  # Workarounds for various client bugs:
  #   outlook-no-nuls:
  #     Outlook and Outlook Express hang if mails contain NUL characters.
  #     This setting replaces them with 0x80 character.
  #   oe-ns-eoh:
  #     Outlook Express and Netscape Mail breaks if end of headers-line is
  #     missing. This option simply sends it if it's missing.
  #pop3_client_workarounds }

##
## Authentication processes
##

# Executable location
#auth_executable = /usr/libexec/dovecot/dovecot-auth

# Set max. process size in megabytes.
#auth_process_size = 256

# Authentication cache size in kilobytes.
#auth_cache_size = 0
# Time to live in seconds for cached data. After this many seconds a cached
# record is forced out of cache.
#auth_cache_ttl = 3600

# Space separated list of realms for SASL authentication mechanisms that 
need
# them. You can leave it empty if you don't want to support multiple realms.
# Many clients simply use the first one listed here, so keep the default 
realm
# first.
#auth_realms 
# Default realm/domain to use if none was specified. This is used for both
# SASL realms and appending @domain to username in plaintext logins.
#auth_default_realm 
# List of allowed characters in username. If the user-given username 
contains
# a character not listed in here, the login automatically fails. This is 
just
# an extra check to make sure user can't exploit any potential quote 
escaping
# vulnerabilities with SQL/LDAP databases. If you want to allow all 
characters,
# set this value to empty.
#auth_username_chars = 
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_@

# Username character translations before it's looked up from databases. The
# value contains series of from -> to characters. For example
"#@/@" means
# that '#' and '/' characters are translated to '@'.
#auth_username_translation 
# Username to use for users logging in with ANONYMOUS SASL mechanism
#auth_anonymous_username = anonymous

# More verbose logging. Useful for figuring out why authentication isn't
# working.
auth_verbose = yes

# Even more verbose logging for debugging purposes. Shows for example SQL
# queries.
#auth_debug = no

# Maximum number of dovecot-auth worker processes. They're used to execute
# blocking passdb and userdb queries (eg. MySQL and PAM). They're
# automatically created and destroyed as needed.
#auth_worker_max_count = 30

auth default {
  # Space separated list of wanted authentication mechanisms:
  #   plain digest-md5 cram-md5 apop anonymous
  mechanisms = plain

  #
  # Password database is used to verify user's password (and nothing more).
  # You can have multiple passdbs and userdbs. This is useful if you want to
  # allow both system users (/etc/passwd) and virtual users to login without
  # duplicating the system users into virtual database.
  #
  # http://wiki.dovecot.org/Authentication
  #

  # PAM authentication. Preferred nowadays by most systems.
  # Note that PAM can only be used to verify if user's password is correct,
  # so it can't be used as userdb. If you don't want to use a separate
user
  # database (passwd usually), you can use static userdb.
  passdb pam {
    # [-session] [<service name>]
    #
    # -session makes Dovecot open and immediately close PAM session. Some
    # PAM plugins need this to work.
    #
    # If service name is "*", it means the authenticating service name
    # is used, eg. pop3 or imap.
    args = imap
    #args = dovecot
  }

  # /etc/passwd or similar, using getpwnam()
  # In many systems nowadays this uses Name Service Switch, which is
  # configured in /etc/nsswitch.conf.
  #passdb passwd {
  #}

  # /etc/shadow or similiar, using getspnam(). Deprecated by PAM nowadays.
  #passdb shadow {
  #}

  # passwd-like file with specified location
  #passdb passwd-file {
    # Path for passwd-file
    #args   #}

  # checkpassword executable authentication
  #passdb checkpassword {
    # Path for checkpassword binary
    #args   #}

  # SQL database
  #passdb sql {
    # Path for SQL configuration file, see doc/dovecot-sql.conf for example
    #args   #}

  # LDAP database
  #passdb ldap {
    # Path for LDAP configuration file, see doc/dovecot-ldap.conf for 
example
    #args   #}

  # vpopmail authentication
  #passdb vpopmail {
  #}

  #
  # User database specifies where mails are located and what user/group IDs
  # own them. For single-UID configuration use "static".
  #
  # http://wiki.dovecot.org/Authentication
  # http://wiki.dovecot.org/VirtualUsers
  #

  # /etc/passwd or similar, using getpwnam()
  # In many systems nowadays this uses Name Service Switch, which is
  # configured in /etc/nsswitch.conf.
  userdb passwd {
  }

  # passwd-like file with specified location
  #userdb passwd-file {
    # Path for passwd-file
    #args   #}

  # static settings generated from template
  #userdb static {
    # Template for settings. Can return anything a userdb could normally
    # return, eg.: uid, gid, home, mail, nice
    #
    # A few examples:
    #
    #  args = uid=500 gid=500 home=/var/mail/%u
    #  args = uid=500 gid=500 home=/home/%u mail=mbox:%h/mail nice=10
    #
    #args   #}

  # SQL database
  #userdb sql {
    # Path for SQL configuration file, see doc/dovecot-sql.conf for example
    #args   #}

  # LDAP database
  #userdb ldap {
    # Path for LDAP configuration file, see doc/dovecot-ldap.conf for 
example
    #args   #}

  # vpopmail
  #userdb vpopmail {
  #}

  # User to use for the process. This user needs access to only user and
  # password databases, nothing else. Only shadow and pam authentication
  # requires roots, so use something else if possible. Note that passwd
  # authentication with BSDs internally accesses shadow files, which also
  # requires roots. Note that this user is NOT used to access mails.
  # That user is specified by userdb above.
  user = root

  # Directory where to chroot the process. Most authentication backends 
don't
  # work if this is set, and there's no point chrooting if auth_user is 
root.
  # Note that valid_chroot_dirs isn't needed to use this setting.
  #chroot 
  # Number of authentication processes to create
  #count = 1

  # Require a valid SSL client certificate or the authentication fails.
  #ssl_require_client_cert = no
}

# It's possible to export the authentication interface to other programs,
# for example SMTP server which supports talking to Dovecot. Client socket
# handles the actual authentication - you give it a username and password
# and it returns OK or failure. So it's pretty safe to allow anyone 
access to
# it. Master socket is used to a) query if given client was successfully
# authenticated, b) userdb lookups.

# listener sockets will be created by Dovecot's master process using the
# settings given inside the auth section
#auth default_with_listener {
#  mechanisms = plain
#  passdb passwd {
#  }
#  userdb pam {
#  }
#  socket listen {
#    master {
#      path = /var/run/dovecot/auth-master
#      #mode = 0600
#      # Default user/group is the one who started dovecot-auth (root)
#      #user #      #group #    }
#    client {
#      path = /var/run/dovecot-auth-client
#      mode = 0660
#    }
#  }
#}

# connect sockets are assumed to be already running, Dovecot's master
# process only tries to connect to them. They don't need any other settings
# than path for the master socket, as the configuration is done elsewhere.
# Note that the client sockets must exist in login_dir.
#auth external {
#  socket connect {
#    master {
#      path = /var/run/dovecot/auth-master
#    }
#  }
#}

Thanks!

Rob