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

2 files changed, 35 insertions, 0 deletions

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
+}