Re: concerning dovecot settings for high volume server

13 Sep 2015

      thanks very much urban. this was very helpful.
i have around 12500 users spread over 3 independent servers each having around 4000+ users
i am using qmailtoaster, vpopmail, spamassassin and dovecot.
in future i am planning to consolidate all using a HA cluster.
if it is ok with you could you kindly share some information about your email server configuration. if you do not wish to put it on the list then you can directly email me.

is your email volume high ?
server hardware to support  28000 users
mailserver software - exim or postfix ??.
antispam software like spamassassin if any

also if you have faced any email re-download issues with dovecot sometimes randomly incase of pop3 users storing emails on the server ?
thanks
rajesh
----- Original Message -----
From: Urban Loesch [mailto:bind@enas.net]
To: dovecot@dovecot.org
Sent: Sun, 13 Sep 2015 09:33:14 +0200
Subject: Re: concerning dovecot settings for high volume server
Hi,
I have running dovecot with about 28k users.
Here comes my relevant config for pop3 and imap from "doveconf -n".
No problems so far.
-- snip --
default_client_limit = 2000
...
service imap-login {
inet_listener imap {
port = 143
}
process_limit = 256
process_min_avail = 50
service_count = 1
}
service imap {
process_limit = 2048
process_min_avail = 50
service_count = 1
vsz_limit = 512 M
}
...
service pop3-login {
inet_listener pop3 {
port = 110
}
process_limit = 256
process_min_avail = 25
service_count = 1
}
service pop3 {
process_limit = 256
process_min_avail = 25
service_count = 1
}
...
protocol imap {
imap_client_workarounds = tb-extra-mailbox-sep
imap_id_log = *
imap_logout_format = bytes=%i/%o session=<%{session}>
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 session=<%{session}>
}
-- snip --
Regards
Urban
Am 12.09.2015 um 20:53 schrieb Rajesh M:
...
hi
centos 6 64 bit
hex core processor with hyperthreading ie display shows 12 cores
16 gb ram
600 gb 15000 rpm drive
we are having around 4000 users on a server
i wish to allow 1500 pop3 and 1500 imap connections simultaneously.
need help regarding the settings to handle the above
imap-login, pop3-login
imap pop3 service settings
i recently i got an error
imap-login: Error: read(imap) failed: Remote closed connection (process_limit reached?)
my current dovecot config file
# 2.2.7: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-431.23.3.el6.x86_64 x86_64 CentOS release 6.5 (Final)
auth_cache_negative_ttl = 0
auth_cache_ttl = 0
auth_mechanisms = plain login digest-md5 cram-md5
default_login_user = vpopmail
disable_plaintext_auth = no
first_valid_gid = 89
first_valid_uid = 89
log_path = /var/log/dovecot.log
login_greeting = ready.
mail_max_userip_connections = 50
mail_plugins = " quota"
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 {
inbox = yes
location =
prefix =
separator = .
type = private
}
passdb {
args = cache_key=%u webmail=127.0.0.1
driver = vpopmail
}
plugin {
quota = maildir:ignore=Trash
quota_rule = ?:storage=0
}
protocols = imap pop3
service imap-login {
client_limit = 256
process_limit = 400
process_min_avail = 4
service_count = 0
vsz_limit = 512 M
}
service pop3-login {
client_limit = 1000
process_limit = 400
process_min_avail = 12
service_count = 0
vsz_limit = 512 M
}
ssl_cert = 
thanks very much,
rajesh