Large jumps in dovecot-uidlist

[Mark]

Since upgrading to Debian Wheezy I have been observing large jumps in
the value stored in dovecot-uidlist. The effect of these jumps is to
confuse some mail clients (Thunderbird, Opera Mail) causing them not to
display messages from a (random?) point in time onwards in the affected
folder.

I have been unable to determine the root cause of these jumps.

What I do know:

1. I never observed the problem while running Debian Squeeze.

2. The only way I have found to fix the issue is to remove all the
dovecot* files from the affected folder and restart dovecot. I have
tried removing various subsets of the dovecot* files but haven't yet
found a subset that works.

3. I first tried upgrading from Squeeze to Wheezy within a few weeks of
the Wheezy release. At that point the problem occurred so frequently
that I couldn't sync my mail client with my mail box. Multiple folders
exhibited this problem and while I was fixing them the problem appeared
in other folders. I was unable to reach a point where the system was
stable so I reverted back to Squeeze.

4. Some time later (I think a year but I am not sure) I tried the
upgrade to Wheezy again. This time the system was stable. After a few
days I noticed that the problem was still occurring but less frequently.
Since then I have been fixing the problem as I notice it and
experimenting with various settings (mainly locking related) without
success. I now have a cron job that looks for problematic folders and
fixes them when found.

5. I have updated Dovecot packages to those from Jessie via
wheezy-backports and the problem still occurs.

6. Dovecot is installed along with postfix, amavisd-new, clamav-daemon,
procmail and fetchmail.

7. The mail server is running on a eSATA SheevaPlug that boots of an
external USB drive. All user home dirs (and associated mailboxes) are
located on a LUKS/ext3 encrypted partition.

8. The output of dovecot -n may be found at the end of this mail.

9. Uid values for the three most recent instances of this problem are:
3801596527, 3371927249, 3443181615

10. Some folders seem more susceptible to this problem but I have not
been able to identify any common factors/triggers.

11. The problem occurs - on average - once a day.


I am happy to provide any further information, configure any debug
logging and/or test suggested configuration settings that may help track
down the root cause of this problem.

Any help gratefully appreciated.

Mark


# 2.2.13: /etc/dovecot/dovecot.conf
# OS: Linux 3.2.0-4-kirkwood armv5tel Debian 7.8
mail_debug = yes
mail_location = maildir:~/Maildir
mail_max_userip_connections = 100
namespace {
  inbox = yes
  location =
  mailbox {
    special_use = \Drafts
    name = Drafts
  }
  mailbox {
    special_use = \Junk
    name = Junk
  }
  mailbox {
    special_use = \Sent
    name = Sent
  }
  mailbox {
    special_use = \Sent
    name = Sent Messages
  }
  mailbox {
    special_use = \Trash
    name = Trash
  }
  prefix =
  name = inbox
}
passdb {
  driver = pam
}
protocols = " imap"
service replication-notify-fifo {
  name = aggregator
}
service anvil-auth-penalty {
  name = anvil
}
service auth-worker {
  name = auth-worker
}
service {
  unix_listener {
    group = postfix
    mode = 0666
    user = postfix
    path = /var/spool/postfix/private/auth-client
  }
  name = auth
}
service config {
  name = config
}
service dict {
  name = dict
}
service login/proxy-notify {
  name = director
}
service dns-client {
  name = dns_client
}
service doveadm-server {
  name = doveadm
}
service {
  inet_listener {
    port = 0
    name = imap
  }
  inet_listener {
    port = 993
    ssl = yes
    name = imaps
  }
  process_min_avail = 5
  name = imap-login
}
service imap-urlauth {
  name = imap-urlauth-login
}
service imap-urlauth-worker {
  name = imap-urlauth-worker
}
service token-login/imap-urlauth {
  name = imap-urlauth
}
service {
  executable = imap postlogin
  name = imap
}
service indexer-worker {
  name = indexer-worker
}
service indexer {
  name = indexer
}
service ipc {
  name = ipc
}
service lmtp {
  name = lmtp
}
service log-errors {
  name = log
}
service pop3 {
  name = pop3-login
}
service login/pop3 {
  name = pop3
}
service {
  executable = script-login -d rawlog
  name = postlogin
}
service replicator-doveadm {
  name = replicator
}
service login/ssl-params {
  name = ssl-params
}
service stats-mail {
  name = stats
}
ssl_cert = </etc/ssl/certs/smtpd.crt
ssl_cipher_list = HIGH:MEDIUM:!aNULL:!MD5:!RC4
ssl_key = </etc/ssl/private/smtpd.key
userdb {
  driver = passwd
}
protocol imap {
  service replication-notify-fifo {
    name = aggregator
  }
  service anvil-auth-penalty {
    name = anvil
  }
  service auth-worker {
    name = auth-worker
  }
  service auth-client {
    name = auth
  }
  service config {
    name = config
  }
  service dict {
    name = dict
  }
  service login/proxy-notify {
    name = director
  }
  service dns-client {
    name = dns_client
  }
  service doveadm-server {
    name = doveadm
  }
  service imap {
    name = imap-login
  }
  service imap-urlauth {
    name = imap-urlauth-login
  }
  service imap-urlauth-worker {
    name = imap-urlauth-worker
  }
  service token-login/imap-urlauth {
    name = imap-urlauth
  }
  service login/imap {
    name = imap
  }
  service indexer-worker {
    name = indexer-worker
  }
  service indexer {
    name = indexer
  }
  service ipc {
    name = ipc
  }
  service lmtp {
    name = lmtp
  }
  service log-errors {
    name = log
  }
  service pop3 {
    name = pop3-login
  }
  service login/pop3 {
    name = pop3
  }
  service replicator-doveadm {
    name = replicator
  }
  service login/ssl-params {
    name = ssl-params
  }
  service stats-mail {
    name = stats
  }
}