[Dovecot] BUG: mbox_snarf causes message duplication when two IMAP connections are open

[Robert Lazzurs]

Hello,

I have used dovecot to replace an ageing wu-imap installation using
the mbox_snarf plugin however I have noticed that when we have more
than one client checking the INBOX we then have messages being
duplicated in the INBOX.

Below is the configuration used as requested in the bug report page.
I have confirmed that the duplicates are being caused by dovecot by
doing an strace of both processes that have both the INBOX
(/mail_home/$username/INBOX) and mail spool file
(/var/spool/dovecot/$username) open and delivering a new message
through exim to the mail spool file in /var/spool/dovecot/$username.
I then see in strace first one process check the spool and copy the
message over and then the other processes do the same.

If anyone requires any further information to confirm this bug please
let me know.

Kind regards.

Version: 1.2.1

[root at wine ~]# dovecot -n
# 1.2.1: /etc/dovecot.conf
# OS: Linux 2.6.18-128.el5 i686 CentOS release 5.3 (Final) ext3
protocols: imap
listen: *:10143 *:143
ssl: no
login_dir: /var/run/dovecot/login
login_executable: /usr/libexec/dovecot/imap-login
mail_access_groups: accounts agen directors extsw fax ftpguest imapshared operat
ions personnel sysadmin
mail_privileged_group: mail
mail_location: mbox:/mail_home/%u/:INBOX=/var/spool/dovecot/%u
mail_debug: yes
mbox_dirty_syncs: no
mbox_lazy_writes: no
mail_plugins: mbox_snarf
imap_client_workarounds: tb-extra-mailbox-sep
namespace:
  type: shared
  prefix: shared/
  location: mbox:/mail_home/imapshared/
  list: yes
namespace:
  type: private
  separator: /
  inbox: yes
  list: yes
  subscriptions: yes
namespace:
  type: private
  separator: /
  prefix: mail/
  hidden: yes
  list: no
  subscriptions: yes
namespace:
  type: private
  separator: /
  prefix: ~/mail/
  hidden: yes
  list: no
  subscriptions: yes
namespace:
  type: private
  separator: /
  prefix: ~%u/mail/
  hidden: yes
  list: no
  subscriptions: yes
auth default:
  passdb:
    driver: pam
  userdb:
    driver: passwd
plugin:
  mbox_snarf: /mail_home/%u/INBOX