Hi Rajesh,

our setup looks as follows:

• we are running linux-vserver as virtualization technology

• we have 2 dedicated IMAP/POP3 Proxies in front of 8 dovecot containers.

• totally about 2900 concurrent imap sessions on each imap proxy and about 180 concurrent pop3 sessions

• all dovecot containers are running on the same hardware (no problems until today): DELL PER720 with 2x 200GB RAID 1 SSD's for dovecot indexes, 8x 4TB RAID 10 for maildata, 2x300GB RAID1 for OS 64GB RAM, 2x CPU E5-2640 0 @ 2.50GHz

• HA is Active/Passive with DRBD on 10GBIT dedicated NIC's for all 3 partitions.

• in summary there are about 47k accounts on it.

• 15minutes system load is between 0.5 - 2.5

• mailserver software is always postfix

• amavis with spamassassin and clamav

• opendkim, opendmarc as milter implementations

Front MX and antispam filtering is running on 2 different machines. Mail volume is between 200k and 600k (spam inclusive) per day. We never faced some email re-download, only if the customers changes his mail client. But that's normal.

Hope that helps.

Best Urban

Am 13.09.2015 um 19:35 schrieb Rajesh M:

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.

1. is your email volume high ?
2. server hardware to support 28000 users
3. mailserver software - exim or postfix ??.
4. 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 = </var/qmail/control/servercert.pem ssl_dh_parameters_length = 2048 ssl_key = </var/qmail/control/servercert.pem userdb { args = cache_key=%u quota_template=quota_rule=*:backend=%q driver = vpopmail } protocol imap { imap_client_workarounds = delay-newmail mail_plugins = " quota imap_quota" } protocol pop3 { pop3_client_workarounds = outlook-no-nuls oe-ns-eoh pop3_fast_size_lookups = yes pop3_lock_session = no pop3_no_flag_updates = yes }

thanks very much,

rajesh