[Dovecot] Proxy login failures

[Urban Loesch]

Hi,

I'm using two dovecot pop3/imap proxies in front of our dovecot servers.
Since some days I see many of the following errors in the logs of the two proxy-servers:

...
dovecot: pop3-login: Error: proxy: Remote "IPV6-IP":110 disconnected: Connection closed: Connection reset by peer (state=0): user=<myuser>, 
method=PLAIN, rip=remote-ip, lip=localip
...
dovecot: imap-login: Error: proxy: Remote "IPV6-IP":143 disconnected: Connection closed: Connection reset by peer (state=0): user=<myuser>, 
method=PLAIN, rip=remote-ip, lip=localip

...


When this happens the Client gets the following error from the proxy:
-ERR [IN-USE] Account is temporarily unavailable.


System-details:
OS: Debian Linux
Proxy: 2.0.5-0~auto+23
Backend: 2.0.13-0~auto+54

Have you any idea what could cause this type of error?

Thanks and regards
Urban Loesch


doveconf -n from one of our backendservers:

# 2.0.13 (02d97fb66047): /etc/dovecot/dovecot.conf
# OS: Linux 2.6.38.8-vs2.3.0.37-rc17-rol-em64t-timerp x86_64 Debian 6.0.2 ext4
auth_cache_negative_ttl = 0
auth_cache_size = 40 M
auth_cache_ttl = 12 hours
auth_mechanisms = plain login
auth_username_format = %Lu
auth_verbose = yes
deliver_log_format = msgid=%m: %$ %p %w
disable_plaintext_auth = no
login_trusted_networks = our Proxy IP's (v4 and v6)
mail_gid = mailstore
mail_location = mdbox:/home/vmail/%d/%n:INDEX=/home/dovecotindex/%d/%n
mail_plugins = " quota mail_log notify zlib"
mail_uid = mailstore
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 imapflags notify
mdbox_rotate_size = 5 M
passdb {
   args = /etc/dovecot/dovecot-sql-account.conf
   driver = sql
}
plugin {
   mail_log_events = delete undelete expunge copy mailbox_delete mailbox_rename
   mail_log_fields = uid box msgid size from
   mail_log_group_events = no
   quota = dict:Storage used::file:%h/dovecot-quota
   sieve = ~/.dovecot.sieve
   sieve_dir = ~/sieve
   sieve_extensions = +notify +imapflags
   sieve_max_redirects = 10
   zlib_save = gz
   zlib_save_level = 5
}
protocols = imap pop3 lmtp sieve
service imap-login {
   inet_listener imap {
     port = 143
   }
   service_count = 0
   vsz_limit = 256 M
}
service lmtp {
   inet_listener lmtp {
     address = *
     port = 24
   }
   unix_listener /var/spool/postfix/private/dovecot-lmtp {
     group = postfix
     mode = 0666
     user = postfix
   }
   vsz_limit = 512 M
}
service pop3-login {
   inet_listener pop3 {
     port = 110
   }
   service_count = 0
   vsz_limit = 256 M
}
ssl = no
ssl_cert = </etc/ssl/certs/dovecot.pem
ssl_key = </etc/ssl/private/dovecot.pem
userdb {
   args = /etc/dovecot/dovecot-sql-account.conf
   driver = sql
}
protocol lmtp {
   mail_plugins = " quota mail_log notify zlib sieve zlib"
}
protocol imap {
   imap_client_workarounds = tb-extra-mailbox-sep
   mail_max_userip_connections = 40
   mail_plugins = " quota mail_log notify zlib imap_quota imap_zlib"
}
protocol pop3 {
   mail_plugins = " quota mail_log notify zlib"
   pop3_logout_format = bytes_sent=%o top=%t/%p, retr=%r/%b, del=%d/%m, size=%s uidl_hash=%u
}