[Config] Add MAILDIR_SUB, "Maildir" for new setups by default

[Update] Add MAILDIR_SUB= for updated mailcows
[Dovecot] Read MAILDIR_SUB for mail_home

docker-compose.yml

@@ -164,7 +164,7 @@ services:
             - sogo
 
     dovecot-mailcow:
-      image: mailcow/dovecot:1.64
+      image: mailcow/dovecot:1.65
       build: ./data/Dockerfiles/dovecot
       cap_add:
         - NET_BIND_SERVICE
@@ -188,6 +188,7 @@ services:
         - MAILDIR_GC_TIME=${MAILDIR_GC_TIME:-1440}
         - ACL_ANYONE=${ACL_ANYONE:-disallow}
         - SKIP_SOLR=${SKIP_SOLR:-y}
+        - MAILDIR_SUB=${MAILDIR_SUB:-}
       ports:
         - "${DOVEADM_PORT:-127.0.0.1:19991}:12345"
         - "${IMAP_PORT:-143}:143"