outlook downloading duplicate emails on particular days

[Rajesh M]

hi

centos 6 with qmail toaster and dovecot 2.2.7 for pop3 and imap

i have a strange issue which happens on all 4 of my servers

for POP3 users -- on any random day ie once in a while users spread across multiple domains will face a problem of outlook re-downloading ALL the emails in the inbox -- not just a few duplicate emails but the entire inbox. 

This happens for multiple email users spread across multiple domains sitting in different locations.

i am searching for a solution for the last several months but nothing yet

require help please

my dovecot config file


# Settings for 'stock' qmail-toaster

disable_plaintext_auth = no
default_login_user = vpopmail
mail_max_userip_connections = 50

service imap-login {
  service_count = 0
  client_limit = 256
  process_min_avail = 4
  vsz_limit = 384M
  process_limit = 400
}

service pop3-login {
  service_count = 0
  client_limit = 1000
  process_min_avail = 12
  vsz_limit = 512M
  process_limit = 400

}

auth_cache_size = 0
auth_cache_ttl = 0
auth_cache_negative_ttl = 0
auth_mechanisms = plain login digest-md5 cram-md5
auth_username_format = %Lu

first_valid_uid = 89
first_valid_gid = 89
log_path = /var/log/dovecot.log

login_greeting = ready.

mail_plugins = $mail_plugins quota
plugin/quota = maildir
protocols = imap pop3
ssl_cert = </var/qmail/control/servercert.pem
ssl_key = </var/qmail/control/servercert.pem

# the following will likely be the default at some point
ssl_dh_parameters_length = 2048


namespace {
  inbox = yes
  location =
  prefix =
# prefix = INBOX.
# Use 'prefix = INBOX.' for Courier-IMAP compatible transparent migration.
# This forces all client apps to create subfolders underneath/within
# the inbox instead of adjacent to it. It's not necessary to be that way.
# FWIW, shubes thinks this setting is annoying/rediculous/retarded.
# As a practical example, having no prefix allows mobile users to select
# which folders get synchronized. Otherwise their whole mailbox is
# synchronized, and they have no way to choose which folders they want sync'd.
  separator = .
  type = private
}

passdb {
  args = cache_key=%u webmail=127.0.0.1
  driver = vpopmail
}

protocol imap {
  imap_client_workarounds = "delay-newmail"
  mail_plugins = $mail_plugins imap_quota
}

protocol pop3 {
  pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
  pop3_fast_size_lookups = yes
  pop3_lock_session = no
# pop3_uidl_format = UID%u-%v
pop3_no_flag_updates=yes
}

userdb {
  args = cache_key=%u quota_template=quota_rule=*:backend=%q
  driver = vpopmail
}

plugin {
  quota = maildir:ignore=Trash
  quota_rule = ?:storage=0
}


thanks
raj