Dovecot 2.2.27 proxy - enforcing per client IP connection limits

[Adi Pircalabu]

Hi,

Trying to keep abusive/buggy IMAP clients at bay on a number of Dovecot 
proxy servers, I've reconfigured them to use 
"mail_max_userip_connections = 50" in the "protocol imap" section, 
followed by restarting Dovecot. Yet, I'm still seeing 160+ established 
connections from a single IP address for the same email account. Am I 
missing anything?

# 2.2.27 (c0f36b0): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.4.16 (fed8554)
# OS: Linux 2.6.32-642.4.2.el6.x86_64 x86_64 CentOS release 6.8 (Final)
auth_cache_negative_ttl = 5 mins
auth_cache_size = 16 M
auth_cache_ttl = 18 hours
default_client_limit = 6120
default_process_limit = 500
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 index ihave duplicate mime foreverypart 
extracttext imapflags notify
mbox_write_locks = fcntl
namespace inbox {
   inbox = yes
   location =
   mailbox Drafts {
     special_use = \Drafts
   }
   mailbox Junk {
     special_use = \Junk
   }
   mailbox Sent {
     special_use = \Sent
   }
   mailbox "Sent Messages" {
     special_use = \Sent
   }
   mailbox Trash {
     special_use = \Trash
   }
   prefix =
}
passdb {
   args = /etc/dovecot/dovecot-sql.conf.ext
   driver = sql
}
plugin {
   sieve = file:~/sieve;active=~/.dovecot.sieve
   sieve_extensions = +notify +imapflags
}
protocols = imap pop3 lmtp sieve
service auth {
   client_limit = 6120
}
service imap-login {
   process_limit = 2048
   process_min_avail = 20
   service_count = 0
   vsz_limit = 256 M
}
service imap {
   process_limit = 2048
}
service managesieve-login {
   inet_listener sieve {
     port = 4190
   }
   service_count = 0
   vsz_limit = 128 M
}
service managesieve {
   process_limit = 1024
}
service pop3 {
   process_limit = 1024
}
[...]
protocol imap {
   imap_capability = IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE
   mail_max_userip_connections = 50
}


-- 
Adi Pircalabu