[Dovecot] dovecotadm error

[Michael]

When I use the following command:
doveadm expunge -A mailbox Junk savedbefore 28d

I get:
doveadm(root): Error: User listing returned failure

In the mail log file it says:
dovecot: auth-worker(18549): Error: sql: Iterate query failed: Table 
'system.users' doesn't exist (using built-in default iterate_query: 
SELECT username, domain FROM users)

However this is setup:

dovecot-sql.conf:
iterate_query = SELECT username AS user FROM accounts

though I have had to comment the following from dovecot.conf:
#iteratedb {
#  args = /usr/local/etc/dovecot/dovecot-sql.conf
#  driver = sql
#}
because it errors on dovecot start up.

I have already spent a bit of time on the Dovecot website and Google 
trying to find an answer. I want to get the expires plugin working.

Any leads please?

dovecot -n

# 2.1.9: /usr/local/etc/dovecot/dovecot.conf
# OS: Linux 2.6.29.6-rt24-smp i686 Slackware 13.1.0
auth_master_user_separator = *
auth_mechanisms = plain login
dict {
   expire = mysql:/usr/local/etc/dovecot/dovecot-dict-expire.conf
   quotadict = mysql:/usr/local/etc/dovecot/dovecot-dict-sql.conf
}
disable_plaintext_auth = no
first_valid_gid = 1000
first_valid_uid = 1000
mail_access_groups = dovecot
mail_location = Maildir:%h/Maildir
mail_plugins = " expire"
mail_privileged_group = mail
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
passdb {
   args = /usr/local/etc/dovecot/dovecot-sql.conf
   driver = sql
}
plugin {
   autocreate = Drafts
   autocreate2 = Junk
   autocreate3 = Sent
   autocreate4 = Trash
   autosubscribe = Drafts
   autosubscribe2 = Junk
   autosubscribe3 = Sent
   autosubscribe4 = Trash
   expire = Junk
   expire_dict = proxy::expire
   quota = dict:user::proxy::quotadict
   sieve = %h/.dovecot.sieve
   sieve_before = /var/lib/dovecot/sieve/before.sieve
   sieve_dir = %h/sieve
   sieve_global_dir = /var/lib/dovecot/sieve/global/
}
protocols = imap pop3 sieve
service auth {
   unix_listener /var/spool/postfix/private/auth {
     group = postfix
     mode = 0660
     user = postfix
   }
   user = root
}
service dict {
   unix_listener dict {
     group = dovecot
     mode = 0660
   }
}
service imap-login {
   inet_listener imap {
     address = DELETED
   }
}
service managesieve-login {
   executable = /usr/local/libexec/dovecot/managesieve-login
}
service managesieve {
   executable = /usr/local/libexec/dovecot/managesieve
}
ssl_cert = </etc/ssl/private/DELETED.pem
ssl_key = </etc/ssl/private/DELETED.pem
userdb {
   args = /usr/local/etc/dovecot/dovecot-sql.lda.conf
   driver = sql
}
userdb {
   args = /usr/local/etc/dovecot/dovecot-sql.conf
   driver = sql
}
protocol imap {
   mail_plugins = autocreate quota imap_quota zlib imap_zlib
}
protocol pop3 {
   mail_plugins = quota
}
protocol lda {
   hostname = DELETED
   mail_plugins = quota sieve
   postmaster_address = DELETED
   sendmail_path = /usr/sbin/sendmail
}
protocol sieve {
   mail_debug = yes
}