why is dovecot "Allowing any password"

[mj]

Hi,

I noticed the following in the logs of our debian wheezy server:
Mar 21 07:13:47 mail dovecot: auth: Debug: 
ldap(username,1.2.3.4,<g2/rF+ZnjAAu5ceg>): bind search: base=CN=Users, DC=samba, 
DC=company, DC=com filter=(&(objectclass=person)(sAMA
ccountName=username)(!(userAccountControl=514)))
Mar 21 07:13:47 mail dovecot: auth: Debug: 
ldap(username,1.2.3.4,<g2/rF+ZnjAAu5ceg>): result: uid=username; uid unused
Mar 21 07:13:47 mail dovecot: auth: Debug: 
ldap(username,1.2.3.4,<g2/rF+ZnjAAu5ceg>): result: uid=username
Mar 21 07:13:48 mail dovecot: auth: ldap(username,1.2.3.4,<g2/rF+ZnjAAu5ceg>): 
invalid credentials (given password: invalid_password)
Mar 21 07:13:48 mail dovecot: auth: Debug: 
static(username,1.2.3.4,<g2/rF+ZnjAAu5ceg>): lookup
Mar 21 07:13:48 mail dovecot: auth: Debug: 
static(username,1.2.3.4,<g2/rF+ZnjAAu5ceg>): allow_nets: Matching for network 
127.0.0.1/32
Mar 21 07:13:48 mail dovecot: auth: 
static(username,1.2.3.4,<g2/rF+ZnjAAu5ceg>): allow_nets check failed: IP not in 
allowed networks
Mar 21 07:13:48 mail dovecot: auth: Debug: 
static(username,1.2.3.4,<g2/rF+ZnjAAu5ceg>): Allowing any password
Mar 21 07:13:54 mail dovecot: auth: Debug: auth client connected (pid=6174)

The line second last line "Allowing any password" comes as a surprise..? 
Why would dovecot Allow any password..?

We had the following bit in our config, but I removed it now:

#passdb {
#  driver = static
#  args = nopassword=y allow_nets=127.0.0.1/32
#}

Could anyone expain the "Allowing any password"?

And lastly our current doveconf -n:

# 2.2.13: /etc/dovecot/dovecot.conf
# OS: Linux 3.2.0-5-amd64 x86_64 Debian 7.11 xfs
auth_debug = yes
auth_debug_passwords = yes
auth_failure_delay = 10 secs
auth_master_user_separator = *
auth_mechanisms = plain login
auth_username_format = %Ln
auth_verbose = yes
auth_verbose_passwords = plain
deliver_log_format = %f | %s | msgid=%m: %$
disable_plaintext_auth = no
lda_mailbox_autocreate = yes
lda_mailbox_autosubscribe = yes
login_greeting = Dovecot ready.
mail_gid = vmail
mail_location = maildir:/var/vmail/%Ln/Maildir:LAYOUT=fs:DIRNAME=mAildir
mail_plugins = acl lazy_expunge zlib quota mail_log notify
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 {
  list = children
  location = 
maildir:/var/vmail/%%u/Maildir:LAYOUT=fs:DIRNAME=mAildir:INDEX=/var/vmail/%u/shared/%%u
  prefix = shared/%%n/
  separator = /
  subscriptions = no
  type = shared
}
namespace inbox {
  inbox = yes
  location = 
  mailbox "Deleted items" {
    special_use = \Trash
  }
  mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Junk {
    special_use = \Junk
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox "Sent items" {
    special_use = \Sent
  }
  mailbox Trash {
    special_use = \Trash
  }
  mailbox inbox {
    auto = subscribe
  }
  prefix = 
  separator = /
  type = private
}
passdb {
  args = /etc/dovecot/master-users
  driver = passwd-file
  master = yes
}
passdb {
  args = /etc/dovecot/dovecot-ldap.conf.ext
  driver = ldap
}
plugin {
  acl = vfile
  acl_shared_dict = file:/var/lib/dovecot/db/shared-mailboxes.db
  mail_log_events = delete undelete expunge copy mailbox_delete mailbox_rename 
append
  mail_log_fields = uid box msgid from subject
  quota = maildir
  quota_rule = ?:storage=5G
  quota_rule2 = Trash:storage=+100M
  quota_warning = storage=97%% quota-warning 97 %u
  quota_warning2 = storage=95%% quota-warning 95 %u
  quota_warning3 = storage=90%% quota-warning 90 %u
  quota_warning4 = storage=85%% quota-warning 85 %u
  quota_warning5 = storage=80%% quota-warning 80 %u
  quota_warning6 = -storage=100%% quota-warning below %u
  sieve = ~/.dovecot.sieve
  sieve_default = /var/lib/dovecot/default.sieve
  sieve_dir = ~/sieve
}
protocols = imap lmtp sieve
service auth {
  unix_listener /var/spool/postfix/private/auth {
    mode = 0666
  }
  unix_listener auth-userdb {
    group = vmail
    mode = 0666
    user = vmail
  }
}
service imap-login {
  process_limit = 500
  process_min_avail = 2
}
service quota-warning {
  executable = script /usr/local/bin/quota-warning.sh
  unix_listener quota-warning {
    user = vmail
  }
  user = dovecot
}
shutdown_clients = no
ssl_ca = </etc/ssl/letsencrypt/fullchain.pem
ssl_cert = </etc/ssl/letsencrypt/cert.pem
ssl_key = </etc/ssl/letsencrypt/key.pem
ssl_protocols = !SSLv2 !SSLv3
userdb {
  args = uid=vmail gid=vmail home=/var/vmail/%n allow_all_users=yes
  driver = static
}
verbose_proctitle = yes
protocol lda {
  mail_plugins = acl lazy_expunge zlib quota mail_log notify sieve quota
}
protocol imap {
  imap_max_line_length = 2 M
  mail_max_userip_connections = 30
  mail_plugins = acl lazy_expunge zlib quota mail_log notify imap_quota imap_acl
}

MJ