Use a local IMAP caching proxy under the webmail.

(Unless the webmail is itself a full IMAP server.) It replaces
RoundCube's own IMAP and message caches.

Dovecot's IMAPC storage backend is not very documented, but provides
smart IMAP proxying. References include:

http://dovecot.org/pipermail/dovecot/2011-January/056975.html
http://wiki2.dovecot.org/HowTo/ImapcProxy
http://wiki2.dovecot.org/Migration/Dsync

12 files changed, 671 insertions, 4 deletions

diff --git a/IMAP.yml b/IMAP.yml
index 0dfc52e..1e55091 100644
--- a/IMAP.yml
+++ b/IMAP.yml
@@ -3,3 +3,11 @@
   hosts: IMAP
   roles:
     - { role: IMAP, inst: IMAP }
+
+- name: Configure IMAP proxies
+  hosts: webmail:!IMAP
+  roles:
+    - IMAP-proxy
+  tags:
+    - imap
+    - dovecot
diff --git a/group_vars/all.yml b/group_vars/all.yml
index 5755086..18c488a 100644
--- a/group_vars/all.yml
+++ b/group_vars/all.yml
@@ -14,3 +14,4 @@ LDA:     { IPv4: lda.fripost.org,      port: 2526 }
 
 LDAP_provider: host1.libvirt.guilhem.org
 NTP_master: host1.libvirt.guilhem.org
+IMAP: host1.libvirt.guilhem.org
diff --git a/roles/IMAP-proxy/files/etc/dovecot/conf.d/10-auth.conf b/roles/IMAP-proxy/files/etc/dovecot/conf.d/10-auth.conf
new file mode 100644
index 0000000..229ac94
--- /dev/null
+++ b/roles/IMAP-proxy/files/etc/dovecot/conf.d/10-auth.conf
@@ -0,0 +1,128 @@
+##
+## Authentication processes
+##
+
+# Disable LOGIN command and all other plaintext authentications unless
+# SSL/TLS is used (LOGINDISABLED capability). Note that if the remote IP
+# matches the local IP (ie. you're connecting from the same computer), the
+# connection is considered secure and plaintext authentication is allowed.
+disable_plaintext_auth = yes
+
+# Authentication cache size (e.g. 10M). 0 means it's disabled. Note that
+# bsdauth, PAM and vpopmail require cache_key to be set for caching to be used.
+#auth_cache_size = 0
+# Time to live for cached data. After TTL expires 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 = 1 hour
+# TTL for negative hits (user not found, password mismatch).
+# 0 disables caching them completely.
+#auth_cache_negative_ttl = 1 hour
+
+# 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 = fripost.org
+
+# 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 formatting before it's looked up from databases. You can use
+# the standard variables here, eg. %Lu would lowercase the username, %n would
+# drop away the domain if it was given, or "%n-AT-%d" would change the '@' into
+# "-AT-". This translation is done after auth_username_translation changes.
+auth_username_format = %Lu
+
+# If you want to allow master users to log in by specifying the master
+# username within the normal username string (ie. not using SASL mechanism's
+# support for it), you can specify the separator character here. The format
+# is then <username><separator><master username>. UW-IMAP uses "*" as the
+# separator, so that could be a good choice.
+#auth_master_user_separator =
+
+# Username to use for users logging in with ANONYMOUS SASL mechanism
+#auth_anonymous_username = anonymous
+
+# 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
+
+# Host name to use in GSSAPI principal names. The default is to use the
+# name returned by gethostname(). Use "$ALL" (with quotes) to allow all keytab
+# entries.
+#auth_gssapi_hostname =
+
+# Kerberos keytab to use for the GSSAPI mechanism. Will use the system
+# default (usually /etc/krb5.keytab) if not specified. You may need to change
+# the auth service to run as root to be able to read this file.
+#auth_krb5_keytab = 
+
+# Do NTLM and GSS-SPNEGO authentication using Samba's winbind daemon and
+# ntlm_auth helper. <doc/wiki/Authentication/Mechanisms/Winbind.txt>
+#auth_use_winbind = no
+
+# Path for Samba's ntlm_auth helper binary.
+#auth_winbind_helper_path = /usr/bin/ntlm_auth
+
+# Time to delay before replying to failed authentications.
+#auth_failure_delay = 2 secs
+
+# Require a valid SSL client certificate or the authentication fails.
+#auth_ssl_require_client_cert = no
+
+# Take the username from client's SSL certificate, using 
+# X509_NAME_get_text_by_NID() which returns the subject's DN's
+# CommonName. 
+#auth_ssl_username_from_cert = no
+
+# Space separated list of wanted authentication mechanisms:
+#   plain login digest-md5 cram-md5 ntlm rpa apop anonymous gssapi otp skey
+#   gss-spnego
+# NOTE: See also disable_plaintext_auth setting.
+auth_mechanisms = plain
+
+##
+## Password and user databases
+##
+
+#
+# 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.
+#
+# <doc/wiki/PasswordDatabase.txt>
+#
+# User database specifies where mails are located and what user/group IDs
+# own them. For single-UID configuration use "static" userdb.
+#
+# <doc/wiki/UserDatabase.txt>
+
+#!include auth-deny.conf.ext
+#!include auth-master.conf.ext
+
+#!include auth-system.conf.ext
+#!include auth-sql.conf.ext
+#!include auth-ldap.conf.ext
+#!include auth-passwdfile.conf.ext
+#!include auth-checkpassword.conf.ext
+#!include auth-vpopmail.conf.ext
+#!include auth-static.conf.ext
+!include auth-imap.conf.ext
diff --git a/roles/IMAP-proxy/files/etc/dovecot/conf.d/10-logging.conf b/roles/IMAP-proxy/files/etc/dovecot/conf.d/10-logging.conf
new file mode 120000
index 0000000..fc1f820
--- /dev/null
+++ b/roles/IMAP-proxy/files/etc/dovecot/conf.d/10-logging.conf
@@ -0,0 +1 @@
+../../../../../IMAP/files/etc/dovecot/conf.d/10-logging.conf
\ No newline at end of file
diff --git a/roles/IMAP-proxy/files/etc/dovecot/conf.d/10-mail.conf b/roles/IMAP-proxy/files/etc/dovecot/conf.d/10-mail.conf
new file mode 100644
index 0000000..f106af5
--- /dev/null
+++ b/roles/IMAP-proxy/files/etc/dovecot/conf.d/10-mail.conf
@@ -0,0 +1,362 @@
+##
+## 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 = imapc:~/imapc
+
+# 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 = yes
+
+# 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 = imapproxy
+mail_gid = imapproxy
+
+# 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
+
+##
+## 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
+
+# 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.
+#mail_nfs_storage = no
+# Mail index files also exist in NFS. Setting this to yes requires
+# mmap_disable=yes and fsync_disable=no.
+#mail_nfs_index = 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. 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 = virtual
+
+##
+## 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.
+#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
+
+##
+## 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.
+#mbox_read_locks = fcntl
+#mbox_write_locks = dotlock fcntl
+
+# 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.
+
+# 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.
+#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}
diff --git a/roles/IMAP-proxy/files/etc/dovecot/conf.d/10-master.conf b/roles/IMAP-proxy/files/etc/dovecot/conf.d/10-master.conf
new file mode 100644
index 0000000..ad9b08f
--- /dev/null
+++ b/roles/IMAP-proxy/files/etc/dovecot/conf.d/10-master.conf
@@ -0,0 +1,77 @@
+#default_process_limit = 100
+#default_client_limit = 1000
+
+# Default VSZ (virtual memory size) limit for service processes. This is mainly
+# intended to catch and kill processes that leak memory before they eat up
+# everything.
+#default_vsz_limit = 256M
+
+# Login user is internally used by login processes. This is the most untrusted
+# user in Dovecot system. It shouldn't have access to anything at all.
+default_login_user = dovenull
+
+# Internal user is used by unprivileged processes. It should be separate from
+# login user, so that login processes can't disturb other processes.
+default_internal_user = dovecot
+
+service imap-login {
+  inet_listener imap {
+    address = 127.0.0.1
+    port = 143
+    ssl = no
+  }
+  inet_listener imaps {
+    port = 0
+  }
+
+  # Number of connections to handle before starting a new process. Typically
+  # the only useful values are 0 (unlimited) or 1. 1 is more secure, but 0
+  # is faster. <doc/wiki/LoginProcess.txt>
+  service_count = 1
+
+  # Number of processes to always keep waiting for more connections.
+  #process_min_avail = 0
+
+  # If you set service_count=0, you probably need to grow this.
+  #vsz_limit = $default_vsz_limit
+}
+
+service imap {
+  # Most of the memory goes to mmap()ing files. You may need to increase this
+  # limit if you have huge mailboxes.
+  #vsz_limit = $default_vsz_limit
+
+  # Max. number of IMAP processes (connections)
+  #process_limit = 1024
+}
+
+service auth {
+  # auth_socket_path points to this userdb socket by default. It's typically
+  # used by dovecot-lda, doveadm, possibly imap process, etc. Users that have
+  # full permissions to this socket are able to get a list of all usernames and
+  # get the results of everyone's userdb lookups.
+  #
+  # The default 0666 mode allows anyone to connect to the socket, but the
+  # userdb lookups will succeed only if the userdb returns an "uid" field that
+  # matches the caller process's UID. Also if caller's uid or gid matches the
+  # socket's uid or gid the lookup succeeds. Anything else causes a failure.
+  #
+  # To give the caller full permissions to lookup all users, set the mode to
+  # something else than 0666 and Dovecot lets the kernel enforce the
+  # permissions (e.g. 0777 allows everyone full permissions).
+  unix_listener auth-userdb {
+    #mode = 0666
+    #user = $default_internal_user
+    #group =
+  }
+
+  # Auth process is run as this user.
+  user = $default_internal_user
+}
+
+service auth-worker {
+  # Auth worker process is run as root by default, so that it can access
+  # /etc/shadow. If this isn't necessary, the user should be changed to
+  # $default_internal_user.
+  user = $default_internal_user
+}
diff --git a/roles/IMAP-proxy/files/etc/dovecot/conf.d/15-mailboxes.conf b/roles/IMAP-proxy/files/etc/dovecot/conf.d/15-mailboxes.conf
new file mode 120000
index 0000000..1883eda
--- /dev/null
+++ b/roles/IMAP-proxy/files/etc/dovecot/conf.d/15-mailboxes.conf
@@ -0,0 +1 @@
+../../../../../IMAP/files/etc/dovecot/conf.d/15-mailboxes.conf
\ No newline at end of file
diff --git a/roles/IMAP-proxy/handlers/main.yml b/roles/IMAP-proxy/handlers/main.yml
new file mode 100644
index 0000000..45f817d
--- /dev/null
+++ b/roles/IMAP-proxy/handlers/main.yml
@@ -0,0 +1,3 @@
+---
+- name: Restart Dovecot
+  service: name=dovecot state=restarted
diff --git a/roles/IMAP-proxy/tasks/main.yml b/roles/IMAP-proxy/tasks/main.yml
new file mode 100644
index 0000000..c630cfd
--- /dev/null
+++ b/roles/IMAP-proxy/tasks/main.yml
@@ -0,0 +1,51 @@
+- name: Install Dovecot
+  apt: pkg={{ item }}
+  with_items:
+    - dovecot-core
+    - dovecot-imapd
+
+- name: Create a user 'imapproxy'
+  user: name=imapproxy system=yes
+        home=/home/imapproxy
+        shell=/bin/false
+        password=!
+        state=present
+
+- name: Create a home directory for user 'imapproxy'
+  file: path=/home/imapproxy
+        state=directory
+        owner=imapproxy group=imapproxy
+        mode=0700
+
+- name: Configure Dovecot (1)
+  copy: src=etc/dovecot/conf.d/{{ item }}
+        dest=/etc/dovecot/conf.d/{{ item }}
+        owner=root group=root
+        mode=0644
+  register: r1
+  with_items:
+    - 10-auth.conf
+    - 10-logging.conf
+    - 10-mail.conf
+    - 10-master.conf
+    - 15-mailboxes.conf
+  notify:
+    - Restart Dovecot
+
+- name: Configure Dovecot (2)
+  template: src=etc/dovecot/conf.d/{{ item }}.j2
+            dest=/etc/dovecot/conf.d/{{ item }}
+            owner=root group=root
+            mode=0644
+  register: r2
+  with_items:
+    - 20-imapc.conf
+    - auth-imap.conf.ext
+  notify:
+    - Restart Dovecot
+
+- name: Start Dovecot
+  service: name=dovecot state=started
+  when: not (r1.changed or r2.changed)
+
+- meta: flush_handlers
diff --git a/roles/IMAP-proxy/templates/etc/dovecot/conf.d/20-imapc.conf.j2 b/roles/IMAP-proxy/templates/etc/dovecot/conf.d/20-imapc.conf.j2
new file mode 100644
index 0000000..a6b70c6
--- /dev/null
+++ b/roles/IMAP-proxy/templates/etc/dovecot/conf.d/20-imapc.conf.j2
@@ -0,0 +1,18 @@
+# Smart IMAP proxying with imapc storage
+# 
+# http://dovecot.org/pipermail/dovecot/2011-January/056975.html
+# http://wiki2.dovecot.org/HowTo/ImapcProxy
+# http://wiki2.dovecot.org/Migration/Dsync
+
+imapc_host = {{ IMAP }}
+imapc_port = 143
+imapc_user = %u
+
+# Read multiple mails in parallel, improves performance
+mail_prefetch_count = 20
+
+# The list of valid features can be found there
+# http://hg.dovecot.org/dovecot-2.1/file/f572fbafb445/src/lib-storage/index/imapc/imapc-settings.c
+# (in the struct 'imapc_feature_list imapc_feature_list')
+imapc_features = rfc822.size
+
diff --git a/roles/IMAP-proxy/templates/etc/dovecot/conf.d/auth-imap.conf.ext.j2 b/roles/IMAP-proxy/templates/etc/dovecot/conf.d/auth-imap.conf.ext.j2
new file mode 100644
index 0000000..5e2b28c
--- /dev/null
+++ b/roles/IMAP-proxy/templates/etc/dovecot/conf.d/auth-imap.conf.ext.j2
@@ -0,0 +1,17 @@
+# Authentication via remote IMAP server. Included from auth.conf.
+#
+# <doc/wiki/PasswordDatabase.IMAP.txt>
+
+passdb {
+  driver         = imap
+  args           = host={{ IMAP }} port=143
+  default_fields = userdb_imapc_user=%u userdb_imapc_password=%w
+}
+
+# "prefetch" user database means that the passdb already provided the
+# needed information and there's no need to do a separate userdb lookup.
+# <doc/wiki/UserDatabase.Prefetch.txt>
+userdb {
+  driver         = prefetch
+  default_fields = home=/home/imapproxy/%d/%n
+}
diff --git a/roles/webmail/tasks/roundcube.yml b/roles/webmail/tasks/roundcube.yml
index e76b896..21d4dff 100644
--- a/roles/webmail/tasks/roundcube.yml
+++ b/roles/webmail/tasks/roundcube.yml
@@ -23,10 +23,10 @@
     # Logging/Debugging
     - { var: smtp_log,               value: "FALSE" }
     # IMAP
-    - { var: default_host,           value: "'ssl://imap.fripost.org'" }
-    - { var: imap_auth_type,         value: "'plain'"                  }
-    - { var: imap_cache,             value: "'db'"                     }
-    - { var: message_cache,          value: "'db'"                     }
+    - { var: default_host,           value: "'localhost'" }
+    - { var: imap_auth_type,         value: "'plain'"     }
+    - { var: imap_cache,             value: "null"        }
+    - { var: message_cache,          value: "null"        }
     # SMTP
     - { var: smtp_server,            value: "localhost" }
     - { var: smtp_port,              value: "2580"      }