Pop3 service stops responding

[Victor Benincasa]

Hello Mike,

Same thing here with one of our servers on the last week, but it only 
affected
IMAP service and local connections.

The dovecot was not responding about 10% of attempted connections.

We could not find any hints in the logs, and the problem was unrelated to
connections limit or dovecot configuration (we also tried the default 
setting).

Nothing solved the problem (service restart, default config, etc) only a 
server
reboot.

CentOS 6.6 x64
Dovecot 2.2.18


*Victor Benincasa*
CIO / CTO :: Networks, Apps, Systems, Security, High-end support


On 02/06/2015 04:35, Mike Eriksson wrote:
> Hi!
>
> I have problem with the pop3 service stops responding at random intervals
> on my server. We started to notice this problem as we're running icinga to
> check the imap & pop3 service.
>
> When icinga reports that the service is down. We try to telnet to the
> server on port 110 but it refuses the connection.
>
> I've checked the netstat during this time and it's listens on port 110. My
> first thought we were hitting the max connections and similar.
>
> Changed login_max_connections from 128 to 256. Didnt solve the problem.
>
> Started the debug on the dovecot server but could not see anything in the
> logs. Also the error log or the syslog dosnt report anything that I can see.
>
> Best thing would of course be to start and upgrade the software and
> os(Debian 5) but I'm not comfortable upgrading it at the moment as my
> knowledge about dovecot / postfix isn't great.
>
> Do you have any idéas how to move forward?
>
> dovecot -n
> # 1.0.15: /etc/dovecot/dovecot.conf
> base_dir: /var/run/dovecot/
> log_path: /var/log/dovecot-error.log
> info_log_path: /var/log/dovecot-info.log
> log_timestamp: %Y-%m-%d %H:%M:%S
> protocols: pop3 imap imaps pop3s
> ssl_cipher_list: ALL:!LOW
> disable_plaintext_auth: no
> login_dir: /var/run/dovecot//login
> login_executable(default): /usr/lib/dovecot/imap-login
> login_executable(imap): /usr/lib/dovecot/imap-login
> login_executable(pop3): /usr/lib/dovecot/pop3-login
> login_max_processes_count: 256
> first_valid_uid: 1090
> last_valid_uid: 1090
> first_valid_gid: 1090
> last_valid_gid: 1090
> mail_privileged_group: mail
> mail_location: maildir:~/Maildir
> mail_executable(default): /usr/lib/dovecot/imap
> mail_executable(imap): /usr/lib/dovecot/imap
> mail_executable(pop3): /usr/lib/dovecot/pop3
> mail_plugins(default): quota imap_quota
> mail_plugins(imap): quota imap_quota
> mail_plugins(pop3): quota
> mail_plugin_dir(default): /usr/lib/dovecot/modules/imap
> mail_plugin_dir(imap): /usr/lib/dovecot/modules/imap
> mail_plugin_dir(pop3): /usr/lib/dovecot/modules/pop3
> pop3_uidl_format(default):
> pop3_uidl_format(imap):
> pop3_uidl_format(pop3): %08Xu%08Xv
> auth default:
>    username_chars:
> abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_@%
>    username_translation: %@
>    username_format: %Lu
>    passdb:
>      driver: sql
>      args: /etc/dovecot/dovecot-sql.conf
>    userdb:
>      driver: passwd
>    userdb:
>      driver: sql
>      args: /etc/dovecot/dovecot-sql.conf
>    socket:
>      type: listen
>      client:
>        path: /var/spool/postfix/private/auth
>        mode: 432
>        user: postfix
>        group: postfix
>      master:
>        path: /var/run/dovecot/auth-master
>        mode: 384
>        user: vmail
>        group: vmail
> plugin:
>    quota: maildir
>    sieve_global_path: /etc/dovecot/sieve_scripts/spam-sort.sieve
>
> login_max_processes_count: 256
> login_max_connections: 256
> max_mail_processes: 1024
>
> Best Regards
> Mike