[Dovecot] Setting hierarchy separator

[ksrini9 at yahoo.com]

I am trying to convert my maildir mail store to dbox using dsync (using "dsync -u username convert dbox:/mailstore2/dbox").  
 
I get the following error message:
 
dsync(root): Fatal: Mail locations must use the same virtual mailbox hierarchy separator (specify separator for the default namespace).
 
My problem is that I do not know how to set separator in 10-mail.conf.  I would appreciate any pointers.  
 
Here is the output from dovecot -n:
 
# 2.0.3: /usr/local/etc/dovecot/dovecot.conf
# OS: Linux 2.6.18-194.el5 x86_64 Red Hat Enterprise Linux Server release 5.5 (Tikanga) ext3
auth_cache_size = 20480
auth_cache_ttl = 7200 s
base_dir = /var/run/dovecot/
disable_plaintext_auth = no
listen = *
log_path = /var/log/dovecot.log
mail_location = maildir:/mailstore/dovecot/maildir/%u
maildir_very_dirty_syncs = yes
passdb {
  args = /etc/passwd.dovecot
  driver = passwd-file
}
postmaster_address = postmaster at localhost
protocols = imap
service imap-login {
  inet_listener imap {
    port = 143
  }
  service_count = 0
  vsz_limit = 67108864
}
ssl = no
userdb {
  driver = passwd
}

 
Thanks,
 
Srini