/etc/dovecot/conf.d/10-mail.conf

##
## 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>
#
#mail_location = mbox:~/mail:INBOX=/var/mail/%u

# 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.
namespace inbox {
  # 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 = yes

  # 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
}

# 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
#}
# Should shared INBOX be visible as "shared/user" or "shared/user/INBOX"?
#mail_shared_explicit_inbox = no

# 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>
#mail_uid =
#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.
#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).
#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/.
#mail_full_filesystem_access = no

# Dictionary for key=value mailbox attributes. Currently used by URLAUTH, but
# soon intended to be used by METADATA as well.
#mail_attribute_dict =

##
## Mail processes
##

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

# 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.
#dotlock_use_excl = yes

# 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)
#mail_fsync = optimized

# 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.
#lock_method = fcntl

# Directory in which LDA/LMTP temporarily stores incoming mails >128 kB.
#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.
#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

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

# UNIX socket path to master authentication server to find users.
# This is used by imap (for shared users) and lda.
#auth_socket_path = /var/run/dovecot/auth-userdb

# Directory where to look up mail plugins.
#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.
#mail_plugins =

##
## Mailbox handling optimizations
##

# Mailbox list indexes can be used to optimize IMAP STATUS commands. They are
# also required for IMAP NOTIFY extension to be enabled.
#mailbox_list_index = no

# 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 can also use dnotify, inotify and
# kqueue to find out immediately when changes occur.
#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.
#mail_save_crlf = no

# Max number of mails to keep open and prefetch to memory. This only works with
# some mailbox formats and/or operating systems.
#mail_prefetch_count = 0

# How often to scan for stale temporary files and delete them (0 = never).
# These should exist only after Dovecot dies in the middle of saving mails.
#mail_temp_scan_interval = 1w

##
## 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)
#maildir_stat_dirs = no

# 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.
#maildir_copy_with_hardlinks = yes

# 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.
#maildir_very_dirty_syncs = no

# If enabled, Dovecot doesn't use the S=<size> in the Maildir filenames for
# getting the mail's physical size, except when recalculating Maildir++ quota.
# This can be useful in systems where a lot of the Maildir filenames have a
# broken size. The performance hit for enabling this is very small.
#maildir_broken_filename_sizes = no

# Always move mails from new/ directory to cur/, even when the \Recent flags
# aren't being reset.
#maildir_empty_new = 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.
#  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.
#
# The Debian value for mbox_write_locks differs from upstream Dovecot. It is
# changed to be compliant with Debian Policy (section 11.6) for NFS safety.
#       Dovecot: mbox_write_locks = dotlock fcntl
#       Debian:  mbox_write_locks = fcntl dotlock
#
#mbox_read_locks = fcntl
#mbox_write_locks = fcntl dotlock

# Maximum time to wait for lock (all of them) before aborting.
#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.
#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.
#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 (e.g. 100k), don't write index files.
# If an index file already exists it's still read, just not updated.
#mbox_min_index_size = 0

# Mail header selection algorithm to use for MD5 POP3 UIDLs when
# pop3_uidl_format=%m. For backwards compatibility we use apop3d inspired
# algorithm, but it fails if the first Received: header isn't unique in all
# mails. An alternative algorithm is "all" that selects all headers.
#mbox_md5 = apop3d

##
## mdbox-specific settings
##

# Maximum dbox file size until it's rotated.
#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.
#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).
#mdbox_preallocate_space = no

##
## 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.

# 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.
#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
#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
#mail_attachment_hash = %{sha1}