[Dovecot] Mbox corruption - Inbox beginning with 'FFrom' or 'FrFrom'

[Henri Khou]

Hi,

Since the 23rd of March, we encounter mailbox corruption for some users 
(15 out of 5000) using POP mainly via Thunderbird.
Symptoms are :

    -users can login but fail to receive new mails and fail to read 
their inbox
    -Dovecot.log : ar 29 11:00:06 Error: POP3(user_login): Couldn't init 
INBOX: Mailbox isn't a valid mbox
    -The mailbox start with either 'FFrom or 'FrFrom'

We can temporarily fix the issue by manually editing the mailbox so that 
it begins with a proper 'From'.
For some users, the problem reoccurred after we apply this workaround.
I have to mention that this server has been running fine since almost a 
year with the current  hardware and software configuration.

Does anybody has an idea regarding this issue?

Many thanks

Henri

=============================
System :        openSUSE 11.1 (x86_64)
Local FS :     ReiserFS

dovecot -n
# 1.1.7: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.27.37-0.1-default x86_64 openSUSE 11.1 (x86_64)
log_path: /var/log/dovecot.log
syslog_facility: local7
protocols: imap imaps pop3 pop3s managesieve
listen(default): *
listen(imap): *
listen(pop3): *
listen(managesieve): *:2000
ssl_cert_file: /etc/ssl/certs/cert_742088754.pem
ssl_key_file: /etc/ssl/private/imap.ehess.fr.key
disable_plaintext_auth: no
verbose_ssl: yes
login_dir: /var/run/dovecot/login
login_executable(default): /usr/lib/dovecot/imap-login
login_executable(imap): /usr/lib/dovecot/imap-login
login_executable(pop3): /usr/lib/dovecot/pop3-login
login_executable(managesieve): /usr/lib/dovecot/managesieve-login
login_greeting_capability(default): yes
login_greeting_capability(imap): yes
login_greeting_capability(pop3): no
login_greeting_capability(managesieve): no
mail_max_userip_connections(default): 10
mail_max_userip_connections(imap): 10
mail_max_userip_connections(pop3): 3
mail_max_userip_connections(managesieve): 10
mail_uid: mail
mail_gid: mail
mail_location: mbox:~/:INBOX=/var/mail/%u:INDEX=/var/run/dovecot/indexes/%n
mbox_lazy_writes: no
mail_executable(default): /usr/lib/dovecot/imap
mail_executable(imap): /usr/lib/dovecot/imap
mail_executable(pop3): /usr/lib/dovecot/pop3
mail_executable(managesieve): /usr/lib/dovecot/managesieve
mail_plugins(default): quota imap_quota trash expire
mail_plugins(imap): quota imap_quota trash expire
mail_plugins(pop3): quota
mail_plugins(managesieve):
mail_plugin_dir(default): /usr/lib64/dovecot/modules/imap
mail_plugin_dir(imap): /usr/lib64/dovecot/modules/imap
mail_plugin_dir(pop3): /usr/lib64/dovecot/modules/pop3
mail_plugin_dir(managesieve): /usr/lib64/dovecot/modules/managesieve
imap_client_workarounds(default): outlook-idle delay-newmail
imap_client_workarounds(imap): outlook-idle delay-newmail
imap_client_workarounds(pop3):
imap_client_workarounds(managesieve):
pop3_reuse_xuidl(default): no
pop3_reuse_xuidl(imap): no
pop3_reuse_xuidl(pop3): yes
pop3_reuse_xuidl(managesieve): no
pop3_lock_session(default): no
pop3_lock_session(imap): no
pop3_lock_session(pop3): yes
pop3_lock_session(managesieve): no
pop3_client_workarounds(default):
pop3_client_workarounds(imap):
pop3_client_workarounds(pop3): outlook-no-nuls oe-ns-eoh
pop3_client_workarounds(managesieve):
dict_db_config: /etc/dovecot/dovecot-db.conf
sieve_storage(default):
sieve_storage(imap):
sieve_storage(pop3):
sieve_storage(managesieve): ~/sieve
sieve(default):
sieve(imap):
sieve(pop3):
sieve(managesieve): ~/.dovecot.sieve
auth default:
  mechanisms: plain login
  verbose: yes
  debug: yes
  passdb:
    driver: pam
    args: dovecot
  userdb:
    driver: passwd
  socket:
    type: listen
    client:
      path: /var/run/dovecot/auth-client
      mode: 432
    master:
      path: /var/run/dovecot/auth-master
      mode: 384
plugin:
  quota: fs:User quota:user:mount=/var/spool/mail
  quota_rule: *:storage=40M
  quota_rule2: INB0X:storage=250M
  quota_rule3: Trash:storage=20M
  quota_rule4: Spam:ignore
  quota_rule4: Sent:storage=20M
  trash: /etc/dovecot/dovecot-trash.conf
  expire: Trash 7 Spam 1
  expire_dict: proxy::expire
dict:
  expire: db:/var/lib/dovecot/expire.db