Enabling improved_mboxlist_sort
*******************************

You can't enable and disable "improved_mboxlist_sort" on a live
system. You need to dump and load the necessary database after
stopping and before starting the master process.  Rename the original
mailboxes.db out of the way between dumping the old and loading the
new.

Dumping the mailboxes.db file

   ctl_mboxlist -d > /var/tmp/mailboxes.txt
   mv mailboxes.db mailboxes.db.orig
   ctl_mboxlist -u < /var/tmp/mailboxes.txt

If your subscription databases are not in flat files you need to do
something similar. Each user will have his own subscription file. Do
the following for each subscription file.

   cyr_dbtool -C $file skiplist show > $file.TXT
   cyr_dbtool -n $file skiplist set < $file.TXT

The above fragments will overwrite the original file. So you could
redirect to a temporary file and overwrite the database if the import
succeeds.