Hello,
I'm build system with two director/proxy and dual stack network (or
IPv6-only local services)
http://wiki2.dovecot.org/Director say "This also means that a single
director ring must use either IPv4 or IPv6 addresses, but not both at
the same time." OK
All servers have 2 interface (public and local network), and all dual
stack IPv4/IPv6, imap/pop (mail) and lmtp (mx) proxy run in dedicated
server. If network IPv4-only this work fine
IPv6-only or IPv4/IPv6 configs not work (on mail director)
dovecot-2.2.10-5.el7, CentOS Linux release 7.2.1511 (Core)
My configs contain
Directors
listen = IPv4-public1, IPv4-local1, IPv6-public1, IPv6-local1
director_servers = IPv6-local1 IPv6-local2
director_mail_servers = IPv4-public3 IPv4-local3 IPv6-public3 IPv6-local3
service lmtp {
  client_limit = 5
  executable = lmtp -L
  idle_kill = 0
  process_limit = 0
  process_min_avail = 0
  protocol = lmtp
  service_count = 0
  inet_listener lmtp {
    address = IPv6-local1 IPv4-local1
    port = 24
  }
}
# 20-lmtp
lmtp_proxy = yes
service director {
  unix_listener login/director {
    mode = 0666
  }
  fifo_listener login/proxy-notify {
    mode = 0600
  }
  unix_listener director-userdb {
    mode = 0600
  }
  inet_listener {
    address = IPv6-local1
    port = 9090
  }
}
Without line "address =" in service, all services start all listen.
If director contain
service imap-login {
  executable = imap-login director
  idle_kill = 10 secs
  inet_listener imap {
    port = 143
  }
  process_limit = 400
  process_min_avail = 10
  service_count = 0
  vsz_limit = 512 M
}
log after start server
# systemctl status dovecot
? dovecot.service - Dovecot IMAP/POP3 email server
   Loaded: loaded (/usr/lib/systemd/system/dovecot.service; enabled;
vendor preset: disabled)
   Active: active (running) since Thu 2016-01-28 13:12:49 MSK; 5s ago
  Process: 11111 ExecStartPre=/usr/libexec/dovecot/prestartscript
(code=exited, status=0/SUCCESS)
 Main PID: 11114 (dovecot)
   CGroup: /system.slice/dovecot.service
           ??11114 /usr/sbin/dovecot -F
           ??11116 dovecot-director/imap-login director
           ??11117 dovecot-director/anvil [10 connections]
           ??11118 dovecot-director/log
           ??11120 dovecot-director/imap-login director
           ??11121 dovecot-director/imap-login director
           ??11122 dovecot-director/imap-login director
           ??11123 dovecot-director/imap-login director
           ??11124 dovecot-director/imap-login director
           ??11125 dovecot-director/imap-login director
           ??11126 dovecot-director/imap-login director
           ??11127 dovecot-director/imap-login director
           ??11128 dovecot-director/imap-login director
           ??11129 dovecot-director/config
Jan 28 13:12:49 mail systemd[1]: Starting Dovecot IMAP/POP3 email server...
Jan 28 13:12:49 mail systemd[1]: Started Dovecot IMAP/POP3 email server.
Jan 28 13:12:49 mail dovecot[11114]: master: Dovecot v2.2.10 starting
up for imap, pop3 (core dumps disabled)
Jan 28 13:12:49 mail dovecot[11114]: master: Error: service(director):
command startup failed, throttling for 2 secs
Jan 28 13:12:49 mail dovecot[11118]: director: Fatal: Invalid director
port in IPv6-local1
Jan 28 13:12:54 mail dovecot[11118]: director: Fatal: Invalid director
port in IPv6-local1
Jan 28 13:12:54 mail dovecot[11114]: master: Error: service(director):
command startup failed, throttling for 4 secs
# systemctl status dovecot
? dovecot.service - Dovecot IMAP/POP3 email server
   Loaded: loaded (/usr/lib/systemd/system/dovecot.service; enabled;
vendor preset: disabled)
   Active: active (running) since Thu 2016-01-28 13:05:52 MSK; 10min ago
  Process: 10232 ExecStartPre=/usr/libexec/dovecot/prestartscript
(code=exited, status=0/SUCCESS)
 Main PID: 10235 (dovecot)
   CGroup: /system.slice/dovecot.service
           ??10235 /usr/sbin/dovecot -F
           ??10237 dovecot-proxy/anvil [0 connections]
           ??10238 dovecot-proxy/log
Jan 28 13:05:52 mx systemd[1]: Starting Dovecot IMAP/POP3 email server...
Jan 28 13:05:52 mx systemd[1]: Started Dovecot IMAP/POP3 email server.
Jan 28 13:05:52 mx dovecot[10235]: master: Dovecot v2.2.10 starting up
for lmtp (core dumps disabled)
Jan 28 13:06:18 mx dovecot[10238]: director: Fatal: Invalid director
port in IPv6-local1
Jan 28 13:06:18 mx dovecot[10235]: master: Error: service(director):
command startup failed, throttling for 2 secs
Jan 28 13:06:18 mx dovecot[10250]: lmtp(10250): Error: passdb
lookup(mailadm at mx): Disconnected unexpectedly
Jan 28 13:06:20 mx dovecot[10238]: director: Fatal: Invalid director
port in IPv6-local1