[Dovecot] UID 0 problem while issuing an UID THREAD REFS command

[Jesús M. Navarro]

Hi:

This is my first message to this list, so pleased to meet you all.

Using dovecot 2.0.17 from packages at xi.rename-it.nl on a Debian "Squeeze" 
i686.  Mail storage is a local ext3 partition (I attached the output of 
dovecot -n to this message).

I'm having problems on a maildir due to dovecot returning an UID 0 to an UID 
THREAD REFS command:

in <==
TAG5 UID THREAD REFS us-ascii SINCE 18-Jul-2011
out <==
* THREAD (0)(51 52)(53)(54 55 56)(57)(58)(59 60)(61)
TAG5 OK Thread completed.

The issuer is an atmail webmail that after the previous output will try an UID 
FETCH 0 that will fail with a "TAG6 BAD Error in IMAP command UID FETCH: 
Invalid uidset" message.

I think that, as per a previous answer from Timo Sirainen*1, this should be 
considered a dovecot's bug, am I right?  Anyway, what should I try to find why 
is this exactly happening?

TIA

*1 http://www.dovecot.org/list/dovecot/2011-November/061992.html
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# 2.0.17 (687949948a83): /etc/dovecot/dovecot.conf
# OS: Linux 2.6.29-xs5.5.0.15 i686 Debian 6.0.3 ext3
auth_cache_negative_ttl = 10 mins
auth_cache_size = 10 M
auth_debug = yes
auth_debug_passwords = yes
auth_mechanisms = plain login digest-md5 cram-md5
auth_username_chars = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_@:
auth_verbose = yes
disable_plaintext_auth = no
mail_gid = vmail
mail_location = maildir:/var/vmail/%d/%n
mail_plugins = " notify xmpp_pubsub fts fts_squat zlib"
mail_privileged_group = mail
mail_uid = vmail
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date ihave
namespace {
  inbox = yes
  location = 
  prefix = 
  separator = /
}
passdb {
  args = /etc/dovecot/dovecot-sql.conf
  driver = sql
}
plugin {
  enotify_xmpp_jid = dovecot at openfire/%l
  enotify_xmpp_password = [EDITED]
  enotify_xmpp_server = [EDITED]
  enotify_xmpp_use_tls = no
  fts = squat
  fts_squat = partial=4 full=10
  mail_log_events = delete undelete expunge copy mailbox_delete mailbox_rename
  mail_log_fields = uid box msgid size vsize flags
  mail_log_group_events = no
  sieve = ~/.dovecot.sieve
  sieve_after = /var/lib/dovecot.sieve/after.d/
  sieve_before = /var/lib/dovecot.sieve/before.d/
  sieve_dir = ~/sieve
  sieve_global_path = /var/lib/dovecot.sieve/default.sieve
  xmpp_pubsub_events = delete undelete expunge copy mailbox_delete mailbox_rename
  xmpp_pubsub_fields = uid box msgid size vsize flags
}
protocols = " imap lmtp sieve pop3"
service auth {
  unix_listener auth-userdb {
    group = vmail
    mode = 0600
    user = vmail
  }
}
service imap-login {
  service_count = 0
}
service managesieve-login {
  inet_listener sieve {
    port = 4190
  }
  inet_listener sieve_deprecated {
    port = 2000
  }
}
ssl_cert = </etc/dovecot/dovecot.pem
ssl_key = </etc/dovecot/dovecot.pem
userdb {
  driver = prefetch
}
userdb {
  args = /etc/dovecot/dovecot-sql.conf
  driver = sql
}
protocol lmtp {
  mail_plugins = " notify xmpp_pubsub fts fts_squat zlib sieve"
}
protocol lda {
  mail_plugins = " notify xmpp_pubsub fts fts_squat zlib sieve"
}
protocol imap {
  imap_client_workarounds = delay-newmail
}
protocol pop3 {
  pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
}