git subrepo commit (merge) mailcow/src/mailcow-dockerized

subrepo: subdir:   "mailcow/src/mailcow-dockerized"
  merged:   "c7b1dc37"
upstream: origin:   "https://github.com/mailcow/mailcow-dockerized.git"
  branch:   "master"
  commit:   "a366494c"
git-subrepo: version:  "0.4.6"
  origin:   "???"
  commit:   "???"
Change-Id: Id574ecd4e02e3c4fbf8a1efd49be11c0b6d19a3f
diff --git a/mailcow/src/mailcow-dockerized/data/conf/dovecot/dovecot.conf b/mailcow/src/mailcow-dockerized/data/conf/dovecot/dovecot.conf
index b7aca75..159e39f 100644
--- a/mailcow/src/mailcow-dockerized/data/conf/dovecot/dovecot.conf
+++ b/mailcow/src/mailcow-dockerized/data/conf/dovecot/dovecot.conf
@@ -24,6 +24,11 @@
 mail_attachment_fs = crypt:set_prefix=mail_crypt_global:posix:
 mail_attachment_dir = /var/attachments
 mail_attachment_min_size = 128k
+# Significantly speeds up very large mailboxes, but is only safe to enable if
+# you do not manually modify the files in the `cur` directories in
+# mailcowdockerized_vmail-vol-1.
+# https://docs.mailcow.email/manual-guides/Dovecot/u_e-dovecot-performance/
+maildir_very_dirty_syncs = yes
 
 # Dovecot 2.2
 #ssl_protocols = !SSLv3