Plesk Horde or RoundCube webmail shows blank page

Symptoms

• Horde or RoundCube webmail displays a blank page;

• There the following record in /var/log/httpd/error_log file:

  mod_fcgid: stderr: PHP Warning: require_once(): open_basedir restriction in effect. File(/usr/share/psa-roundcube/program/include/iniset.php) is not within the allowed path(s): (xe2x80x9cxe2x80x9d/var/www/vhosts) in /usr/share/psa-roundcube/index.php on line 51

Cause

Wrong settings in
/etc/psa-webmail/horde/horde/php.ini
or
/etc/psa-webmail/roundcube/php.ini
that do not allow webmail to run it’s scripts. 

Resolution

• Log in the server  via SSH.

  Note: if direct SSH access to the server is not possible, contact server administrator for further assistance.

• Remove or comment out 
open_basedir = on in
/etc/psa-webmail/horde/horde/php.ini
or
/etc/psa-webmail/roundcube/php.ini
file.