dovecot/templates/default/conf.d/10-mail.conf.erb

##
## Mailbox locations and namespaces
##

# Location for users' mailboxes. The default is empty, which means that Dovecot
# tries to find the mailboxes automatically. This won't work if the user
# doesn't yet have any mail, so you should explicitly tell Dovecot the full
# location.
#
# If you're using mbox, giving a path to the INBOX file (eg. /var/mail/%u)
# isn't enough. You'll also need to tell Dovecot where the other mailboxes are
# kept. This is called the "root mail directory", and it must be the first
# path given in the mail_location setting.
#
# There are a few special variables you can use, eg.:
#
#   %u - username
#   %n - user part in user@domain, same as %u if there's no domain
#   %d - domain part in user@domain, empty if there's no domain
#   %h - home directory
#
# See doc/wiki/Variables.txt for full list. Some examples:
#
#   mail_location = maildir:~/Maildir
#   mail_location = mbox:~/mail:INBOX=/var/mail/%u
#   mail_location = mbox:/var/mail/%d/%1n/%n:INDEX=/var/indexes/%d/%1n/%n
#
# <doc/wiki/MailLocation.txt>
#
<%= Dovecot::Conf.attribute(@conf, 'mail_location') %>

# 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. Private namespaces
# are for user's personal mails. Shared namespaces are for accessing other
# users' mailboxes that have been shared. Public namespaces are for shared
# mailboxes that are managed by sysadmin. If you create any shared or public
# namespaces you'll typically want to enable ACL plugin also, otherwise all
# users can access all the shared mailboxes, assuming they have permissions
# on filesystem level to do so.
#
# REMEMBER: If you add any namespaces, the default namespace must be added
# explicitly, ie. mail_location does nothing unless you have a namespace
# without a location setting. Default namespace is simply done by having a
# namespace with empty prefix.
<% if @namespaces.kind_of?(Array) and @namespaces.length > 0 -%>
<%   @namespaces.each do |ns| -%>
<%=    Dovecot::Conf.namespace(ns) %>
<%   end -%>
<% else -%>
#namespace {
  # Namespace type: private, shared or public
  #type = private

  # Hierarchy separator to use. You should use the same separator for all
  # namespaces or some clients get confused. '/' is usually a good one.
  # The default however depends on the underlying mail storage format.
  #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
  # mail_location, which is also the default for it.
  #location =

  # There can be only one INBOX, and this setting defines which namespace
  # has it.
  #inbox = no

  # If namespace is hidden, it's not advertised to clients via NAMESPACE
  # extension. You'll most likely also want to set list=no. This is mostly
  # useful when converting from another server with different namespaces which
  # you want to deprecate but still keep working. For example you can create
  # hidden namespaces with prefixes "~/mail/", "~%u/mail/" and "mail/".
  #hidden = no

  # Show the mailboxes under this namespace with LIST command. This makes the
  # namespace visible for clients that don't support NAMESPACE extension.
  # "children" value lists child mailboxes, but hides the namespace prefix.
  #list = yes

  # Namespace handles its own subscriptions. If set to "no", the parent
  # namespace handles them (empty prefix should always have this as "yes")
  #subscriptions = yes
#}
<% end -%>

# Example shared namespace configuration
#namespace {
  #type = shared
  #separator = /

  # Mailboxes are visible under "shared/user@domain/"
  # %%n, %%d and %%u are expanded to the destination user.
  #prefix = shared/%%u/

  # Mail location for other users' mailboxes. Note that %variables and ~/
  # expands to the logged in user's data. %%n, %%d, %%u and %%h expand to the
  # destination user's data.
  #location = maildir:%%h/Maildir:INDEX=~/Maildir/shared/%%u

  # Use the default namespace for saving subscriptions.
  #subscriptions = no

  # List the shared/ namespace only if there are visible shared mailboxes.
  #list = children
#}

# System user and group used to access mails. If you use multiple, userdb
# can override these by returning uid or gid fields. You can use either numbers
# or names. <doc/wiki/UserIds.txt>
<%= Dovecot::Conf.attribute(@conf, 'mail_uid') %>
<%= Dovecot::Conf.attribute(@conf, 'mail_gid') %>

# Group to enable temporarily for privileged operations. Currently this is
# used only with INBOX when either its initial creation or dotlocking fails.
# Typically this is set to "mail" to give access to /var/mail.
<%= Dovecot::Conf.attribute(@conf, 'mail_privileged_group') %>

# Grant access to these supplementary groups for mail processes. Typically
# these are used to set up access to shared mailboxes. Note that it may be
# dangerous to set these if users can create symlinks (e.g. if "mail" group is
# set here, ln -s /var/mail ~/mail/var could allow a user to delete others'
# mailboxes, or ln -s /secret/shared/box ~/mail/mybox would allow reading it).
<%= Dovecot::Conf.attribute(@conf, 'mail_access_groups') %>

# 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/.
<%= Dovecot::Conf.attribute(@conf, 'mail_full_filesystem_access', false) %>

##
## Mail processes
##

# Don't use mmap() at all. This is required if you store indexes to shared
# filesystems (NFS or clustered filesystem).
<%= Dovecot::Conf.attribute(@conf, 'mmap_disable', false) %>

# Rely on O_EXCL to work when creating dotlock files. NFS supports O_EXCL
# since version 3, so this should be safe to use nowadays by default.
<%= Dovecot::Conf.attribute(@conf, 'dotlock_use_excl', true) %>

# When to use fsync() or fdatasync() calls:
#   optimized (default): Whenever necessary to avoid losing important data
#   always: Useful with e.g. NFS when write()s are delayed
#   never: Never use it (best performance, but crashes can lose data)
<%= Dovecot::Conf.attribute(@conf, 'mail_fsync', 'optimized') %>

# Mail storage exists in NFS. Set this to yes to make Dovecot flush NFS caches
# whenever needed. If you're using only a single mail server this isn't needed.
<%= Dovecot::Conf.attribute(@conf, 'mail_nfs_storage', false) %>
# Mail index files also exist in NFS. Setting this to yes requires
# mmap_disable=yes and fsync_disable=no.
<%= Dovecot::Conf.attribute(@conf, 'mail_nfs_index', false) %>

# 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. NFS users: flock doesn't work, remember to change mmap_disable.
<%= Dovecot::Conf.attribute(@conf, 'lock_method', 'fcntl') %>

# Directory in which LDA/LMTP temporarily stores incoming mails >128 kB.
<%= Dovecot::Conf.attribute(@conf, 'mail_temp_dir', '/tmp') %>

# 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.
<%= Dovecot::Conf.attribute(@conf, 'first_valid_uid', 500) %>
<%= Dovecot::Conf.attribute(@conf, '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.
<%= Dovecot::Conf.attribute(@conf, 'first_valid_gid', 1) %>
<%= Dovecot::Conf.attribute(@conf, 'last_valid_gid', 0) %>

# Maximum allowed length for mail keyword name. It's only forced when trying
# to create new keywords.
<%= Dovecot::Conf.attribute(@conf, 'mail_max_keyword_length', 50) %>

# ':' 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, mail_chroot or auth chroot
# settings. If this setting is empty, "/./" in home dirs are ignored.
# 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. <doc/wiki/Chrooting.txt>
<%= Dovecot::Conf.attribute(@conf, '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. If your home directories are prefixed with
# the chroot directory, append "/." to mail_chroot. <doc/wiki/Chrooting.txt>
<%= Dovecot::Conf.attribute(@conf, 'mail_chroot') %>

# UNIX socket path to master authentication server to find users.
# This is used by imap (for shared users) and lda.
<%= Dovecot::Conf.attribute(@conf, 'auth_socket_path', '/var/run/dovecot/auth-userdb') %>

# Directory where to look up mail plugins.
<%= Dovecot::Conf.attribute(@conf, 'mail_plugin_dir', '/usr/lib/dovecot/modules') %>

# Space separated list of plugins to load for all services. Plugins specific to
# IMAP, LDA, etc. are added to this list in their own .conf files.
<%= Dovecot::Conf.attribute(@conf, 'mail_plugins') %>

##
## Mailbox handling optimizations
##

# 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.
<%= Dovecot::Conf.attribute(@conf, '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 can also use dnotify, inotify and
# kqueue to find out immediately when changes occur.
<%= Dovecot::Conf.attribute(@conf, 'mailbox_idle_check_interval', '30 secs') %>

# 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.
<%= Dovecot::Conf.attribute(@conf, 'mail_save_crlf', false) %>

##
## Maildir-specific settings
##

# By default LIST command returns all entries in maildir beginning with a 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)
<%= Dovecot::Conf.attribute(@conf, 'maildir_stat_dirs', false) %>

# When copying a message, do it with hard links whenever possible. This makes
# the performance much better, and it's unlikely to have any side effects.
<%= Dovecot::Conf.attribute(@conf, 'maildir_copy_with_hardlinks', true) %>

# Assume Dovecot is the only MUA accessing Maildir: Scan cur/ directory only
# when its mtime changes unexpectedly or when we can't find the mail otherwise.
<%= Dovecot::Conf.attribute(@conf, 'maildir_very_dirty_syncs', false) %>

##
## 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.
#  dotlock_try: Same as dotlock, but if it fails because of permissions or
#               because there isn't enough disk space, just skip it.
#  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.
<%= Dovecot::Conf.attribute(@conf, 'mbox_read_locks', 'fcntl') %>
<%= Dovecot::Conf.attribute(@conf, 'mbox_write_locks', 'dotlock fcntl') %>

# Maximum time to wait for lock (all of them) before aborting.
<%= Dovecot::Conf.attribute(@conf, 'mbox_lock_timeout', '5 mins') %>

# If dotlock exists but the mailbox isn't modified in any way, override the
# lock file after this much time.
<%= Dovecot::Conf.attribute(@conf, 'mbox_dotlock_change_timeout', '2 mins') %>

# 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.
<%= Dovecot::Conf.attribute(@conf, 'mbox_dirty_syncs', true) %>

# 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.
<%= Dovecot::Conf.attribute(@conf, 'mbox_very_dirty_syncs', false) %>

# 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.
<%= Dovecot::Conf.attribute(@conf, 'mbox_lazy_writes', true) %>

# If mbox size is smaller than this (e.g. 100k), don't write index files.
# If an index file already exists it's still read, just not updated.
<%= Dovecot::Conf.attribute(@conf, 'mbox_min_index_size', 0) %>

##
## mdbox-specific settings
##

# Maximum dbox file size until it's rotated.
<%= Dovecot::Conf.attribute(@conf, 'mdbox_rotate_size', '2M') %>

# Maximum dbox file age until it's rotated. Typically in days. Day begins
# from midnight, so 1d = today, 2d = yesterday, etc. 0 = check disabled.
<%= Dovecot::Conf.attribute(@conf, 'mdbox_rotate_interval', 0) %>

# When creating new mdbox files, immediately preallocate their size to
# mdbox_rotate_size. This setting currently works only in Linux with some
# filesystems (ext4, xfs).
<%= Dovecot::Conf.attribute(@conf, 'mdbox_preallocate_space', false) %>

##
## Mail attachments
##

# sdbox and mdbox support saving mail attachments to external files, which
# also allows single instance storage for them. Other backends don't support
# this for now.

# WARNING: This feature hasn't been tested much yet. Use at your own risk.

# Directory root where to store mail attachments. Disabled, if empty.
#mail_attachment_dir =

# Attachments smaller than this aren't saved externally. It's also possible to
# write a plugin to disable saving specific attachments externally.
<%= Dovecot::Conf.attribute(@conf, 'mail_attachment_min_size', '128k') %>

# Filesystem backend to use for saving attachments:
#  posix : No SiS done by Dovecot (but this might help FS's own deduplication)
#  sis posix : SiS with immediate byte-by-byte comparison during saving
#  sis-queue posix : SiS with delayed comparison and deduplication
<%= Dovecot::Conf.attribute(@conf, 'mail_attachment_fs', 'sis posix') %>

# Hash format to use in attachment filenames. You can add any text and
# variables: %{md4}, %{md5}, %{sha1}, %{sha256}, %{sha512}, %{size}.
# Variables can be truncated, e.g. %{sha256:80} returns only first 80 bits
<%= Dovecot::Conf.attribute(@conf, 'mail_attachment_hash', '%{sha1}') %>