Webmail login issue: Roundcube Connection to storage server failed

Refers to:

  • Plesk 12.5 for Linux
  • Plesk Onyx for Linux
  • Plesk 11.5 for Linux
  • Plesk 12.0 for Linux
  • Plesk 12.5 for Windows

Created:

2016-11-16 13:19:33 UTC

Modified:

2017-02-22 08:58:58 UTC

1

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Webmail login issue: Roundcube Connection to storage server failed

Symptoms

Sometimes, hosting clients cannot log in to Roundcube or using anther IMAP client on Dovecot IMAP server. Valid credentials are used. The following error appears:

Roundcube Connection to storage server failed

In the ' /var/log/maillog ' the following error message can be found:

dovecot: master: Warning: service(imap-login): process_limit (100) reached, client connections are being dropped
...
...
dovecot: service=lda, user=user@example.com, ip=[]. Error: userdb lookup: connect(/var/run/dovecot/auth-userdb) failed: Connection refused
dovecot: lda: Fatal: Internal error occurred. Refer to server log for more information.
postfix/pipe[185750]: E57D84520062: to=<user@example.com>, relay=plesk_virtual, delay=1.7, delays=0.66/0/0/1.1, dsn=4.2.1, status=deferred (Message can not be delivered at this time )

The following errors appear in /var/log/plesk-roundcube/errors log:

[10-Nov-2016 09:16:47 +0100]: <4gtu8jeh> IMAP Error: Login failed for kru@example.com from 203.0.113.4(X-Real-IP: 203.0.113.2). Empty startup greeting (localhost:143) in /usr/share/psa-roundcube/program/lib/Roundcube/rcube_imap.php on line 193 (GET /?_task=mail&_action=search&_filter=ALL&_interval=&_q=ik&_headers=subject%2Cfrom&_scope=base&_mbox=INBOX&_remote=1&_unlock=loading1478765408628&_=1478765335293)

Cause

Dovecot connections limits exhausted

Resolution

  1. Create a file /etc/dovecot/conf.d/99-imap-login.conf with the following content:

    service imap-login {
    process_limit = 200
    process_min_avail = 16
    }
  2. Tune process_limit value according to the server load.

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