dovecot.conf

a very userful email managing service

## Mailbox handling optimizations
##

# 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 = 

# The minimum number of mails in a mailbox before updates are done to cache
# file. This allows optimizing Dovecot's behavior to do less disk writes at
# the cost of more disk reads.
#mail_cache_min_mail_count = 0

# When IDLE command is running, mailbox is checked once in a while to see if
# there are any new mails or other changes. This setting defines the minimum
# time to wait between those checks. Dovecot is however able to use dnotify
# and inotify with Linux to reply immediately after the change occurs.
#mailbox_idle_check_interval = 30

# 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.
# Also note that if other software reads the mboxes/maildirs, they may handle
# the extra CRs wrong and cause problems.
#mail_save_crlf = no

##
## Maildir-specific settings
##

# 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

##
## mbox-specific settings
##

# Which locking methods to use for locking mbox. There are 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 = 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 = 120

# 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

# If mbox size is smaller than this (in kilobytes), don't write index files.
# If an index file already exists it's still read, just not updated.
#mbox_min_index_size = 0

##
## dbox-specific settings
##

# Maximum dbox file size in kilobytes until it's rotated.
#dbox_rotate_size = 2048

# Minimum dbox file size in kilobytes before it's rotated
# (overrides dbox_rotate_days)
#dbox_rotate_min_size = 16

# Maximum dbox file age in days until it's rotated. Day always begins from
# midnight, so 1 = today, 2 = yesterday, etc. 0 = check disabled.
#dbox_rotate_days = 0

##
## IMAP specific settings
##

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

  # IMAP executable location. Changing this allows you to execute other
  # binaries before the imap process is executed.
  #
  # This would write rawlogs into ~/dovecot.rawlog/ directory:
  #   mail_executable = /usr/libexec/dovecot/rawlog /usr/libexec/dovecot/imap
  #
  # This would attach gdb into the imap process and write backtraces into
  # /tmp/gdbhelper.* files:
  #   mail_executable = /usr/libexec/dovecot/gdbhelper /usr/libexec/dovecot/imap
  #
  #mail_executable = /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

  # Support for dynamically loadable plugins. mail_plugins is a space separated
  # list of plugins to load.
  #mail_plugins = 
  #mail_plugin_dir = /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

  # Override the IMAP CAPABILITY response.
  #imap_capability = 

  # 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.
  # The list is space-separated.
  #imap_client_workarounds = outlook-idle
}
  
##
## POP3 specific settings
##

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

  # POP3 executable location. See IMAP's mail_executable above for examples
  # how this could be changed.
  #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

  # If mail has X-UIDL header, use it as the mail's UIDL.
  #pop3_reuse_xuidl = no

  # Keep the mailbox locked for the entire POP3 session.
  #pop3_lock_session = 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
  #  Older Dovecots      : %v.%u
  #  tpop3d              : %Mf
  #
  # Note that Outlook 2003 seems to have problems with %v.%u format which was
  # 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.
  #
  # NOTE: Nowadays this is required to be set explicitly, since the old
  # default was bad but it couldn't be changed without breaking existing
  # installations. %08Xu%08Xv will be the new default, so use it for new
  # installations.
  #
  #pop3_uidl_format = %08Xu%08Xv

  # POP3 logout format string:
  #  %t - number of TOP commands
  #  %p - number of bytes sent to client as a result of TOP command
  #  %r - number of RETR commands
  #  %b - 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/%p, retr=%r/%b, del=%d/%m, size=%s

  # Support for dynamically loadable plugins. mail_plugins is a space separated
  # list of plugins to load.
  #mail_plugins = 
  #mail_plugin_dir = /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.
  # The list is space-separated.
  #pop3_client_workarounds = 
}

##
## LDA specific settings
##

protocol lda {
  # Address to use when sending rejection mails.
  postmaster_address = [e-mail]

  # Hostname to use in various parts of sent mails, eg. in Message-Id.
  # Default is the system's real hostname.
  #hostname = 

  # Support for dynamically loadable plugins. mail_plugins is a space separated
  # list of plugins to load.
  #mail_plugins = 
  #mail_plugin_dir = /usr/lib/dovecot/lda

  # Binary to use for sending mails.
  #sendmail_path = /usr/lib/sendmail

  # UNIX socket path to master authentication server to find users.
  #auth_socket_path = /var/run/dovecot/auth-master
}

##
## 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. 0 means it's disabled.
# Note that bsdauth, PAM and vpopmail require cache_key to be set for caching
# to be used. Also note that currently auth cache doesn't work very well if 
# you're using multiple passdbs with same usernames in them.
#auth_cache_size = 0
# Time to live in seconds for cached data. After this many seconds the cached
# record is no longer used, *except* if the main database lookup returns
# internal failure. We also try to handle password changes automatically: If
# user's previous authentication was successful, but this one wasn't, the
# cache isn't used. For now this works only with plaintext authentication.
#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,