[Dovecot] dotlock error

[Muhammad Yousuf Khan]

i finally manage to control access on public folder by File system permission.
i have 3 test users.

1. tom
2. fmaster
3 . testmail

tom and fmaster are a group called "news-own" and testmail user is a
readonly one.

here is my folder structure ill share dovecot -n output at the end of
this email.

drwxrwxr-t 2 tom     news-own 4.0K Dec  4 19:08 tmp
drwxrwxr-t 2 tom     news-own 4.0K Dec  4 19:08 new
-rwxrwxrwx 1 tom     news-own   68 Dec  4 19:08 dovecot-uidlist
-rw-rw-r-T 1 fmaster news-own  16K Dec  4 19:10 dovecot.index.cache
drwxrwxr-t 2 tom     news-own 4.0K Dec  4 19:15 cur
-rw-rw-r-T 1 tom     news-own 1.1K Dec  4 19:16 dovecot.index.log

everything works fine as far as user fmaster and tom is concern as
they are member of "news-own" and this group own the mailbox now the
problem i face with readonly users.

i am getting this error in /var/log/mail.info (against user testmail)

file_dotlock_create(/public/.News/dovecot-uidlist) failed: Permission
denied (euid=1002(testmail) egid=1002(testmail) missing +w perm:
/public/.News


at first point i saw this error and i could not subscribe to the
folder. and the said log has been generated.

now on second stage i change the dovecot-uidlist file permission to
"1666"  so that testmail user can also write to the file.

now problem starts from here, i see two folder one is News and second
one is News-1 and i don't know from where the second folder showed up.

and when i click on any of the folder my /var/log/mail.info start to
show below massage continuously. until i restart the dovecot service.

file_dotlock_create(/public/.News/dovecot-uidlist) failed: Permission
denied (euid=1002(testmail) egid=1002(testmail) missing +w perm:
/public/.News


i search google and i saw that people suggested to set stickey bit on
which i already did or suggested to stop "dot locking"

so i am here to ask is there any way to solve my said problem with out
disabling dot locking?

or if i stop dot locking what are the consequences?


here i my dovcecot -n


root at mailsrv:/public/.News# dovecot -n
# 1.2.15: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-5-amd64 x86_64 Debian 6.0.6
log_timestamp: %Y-%m-%d %H:%M:%S
ssl_cert_file: /etc/ssl/certs/postfix.pem
ssl_key_file: /etc/ssl/private/postfix.key
login_dir: /var/run/dovecot/login
login_executable: /usr/lib/dovecot/imap-login
mail_privileged_group: mail
mail_location: maildir:~/Maildir:INBOX=~/Maildir/:INDEX=~/Maildir/index
mail_debug: yes
mbox_write_locks: fcntl dotlock
namespace:
  type: private
  separator: /
  inbox: yes
  list: yes
  subscriptions: yes
namespace:
  type: public
  separator: /
  prefix: Shared folders/
  location: maildir:/public
  list: yes
auth default:
  mechanisms: plain login
  passdb:
    driver: pam
  userdb:
    driver: passwd
  socket:
    type: listen
    client:
      path: /var/spool/postfix/private/auth
      mode: 432
      user: postfix
      group: postfix


Thanks in advance, any help or suggestion would be highly appreciated.