Unable to log into Roundcube Webmail: Connection to storage server failed

Symptoms

• An error is received while trying to login to webmail.example.com:

  Connection to storage server failed

• The following errors are found in /var/log/maillog:

  PHP Warning: stream_socket_client(): unable to connect to ssl://localhost:993 (Connection refused) in /usr/share/psa-roundcube/program/lib/Roundcube/rcube_imap_generic.php on line 1060

  IMAP Error: Login failed for jdoe@example.com against localhost from 203.0.113.2 (X-Forwarded-For: 203.0.113.3). Could not connect to ssl://localhost:993: Connection refused in /usr/share/psa-roundcube/program/lib/Roundcube/rcube_imap.php on line 211 (POST /roundcube/?_task=login&_action=login)

• Dovecot service is not listening on port 993 but 9993 instead:

  # netstat -putan | grep 993
  tcp 0 0 127.0.0.1:9993 0.0.0.0:* LISTEN 2715700/dovecot

Cause

Plesk Premium Email extension is installed but partially configured or disabled.

Resolution

Apply one of the following solutions:

• Complete the extension configuration from Plesk > Plesk Premium Email
• Remove it from Extensions > My extensions > Plesk Premium Email > Remove (trash icon button) if not used.