Outdated custom Roundcube configuration causing issues

Symptoms

Servers with a custom Roundcube configuration may display unusual behavior after a Roundcube update, and an error similar to the following may be found in the cPanel error log or the cPanel user's .php.error.log log file. 

PHP Warning:  include(/usr/local/cpanel/base/3rdparty/roundcube/config/cpanel_config.php): Failed to open stream: No such file or directory in /usr/local/cpanel/base/3rdparty/roundcube/config/config.inc.php on line 1452

[18-Jun-2025 14:52:36 +0300]: <57132734> PHP Error: Error loading template for mail in /usr/local/cpanel/base/3rdparty/roundcube/program/include/rcmail_output_html.php on line 804 (GET /cpsess6477695235/3rdparty/roundcube/index.php?_task=mail&_token=L0bS0NWqWe1WgWfdur87dlGg9j9B7Dzy)

Description

Roundcube updates can move, delete, or rename files and may remove features that custom configurations rely on. When Roundcube cannot find the specified files or features, it will throw an error.

Workaround

Remove or adjust the custom configuration.