This question had me stumped for a long while. Months ago I was unable to find the answer and so I just edited /usr/local/cpanel/base/horde/imp/config/mime_drivers.php, specifically changing the section:
$mime_drivers['imp']['html'] = array(
'inline' => false,
to:
$mime_drivers['imp']['html'] = array(
'inline' => true,
As I feared, every time cPanel updated Horde, this change would be lost and my users would complain. Now, I believe I have found a solution. (However Horde has not yet updated so I am unable to tell for sure if this works).
After including imp/config/mime_drivers.php, Horde will check for a directory imp/config/mime_drivers.d/ and, if found, will include() all files ending in .php in that directory. This directory does not exist under cPanel, so it can be created without fear of being overwritten.
The file /usr/local/cpanel/src/3rdparty/gpl/README-horde contains details on how cPanel updates Horde, as well as instructions on customizing Horde. A few relevant excepts of that file give clues as to how to make the customizations I wanted permanently:
During the maintenance phase of /scripts/upcp and
/scripts/maintenance, the webmail script found at
/usr/local/cpanel/install/webmail is executed. This in turn executes
/usr/local/cpanel/bin/update-horde. Presented below is an outline of
steps update-horde performs:
- The Horde installation is wiped clean (rm -rf /usr/local/cpanel/base/horde).
- Using the version specified in update-horde, the appropriate Horde source tarball will be extracted to /usr/local/cpanel/base.
[...]
After determining which tarball to use for the source install, and
extracting it, the update-horde script checks for the following:
o /var/cpanel/horde/overlay.tar
o /var/cpanel/horde/overlay.tar.gz
o /var/cpanel/horde/overlay.$hordever.tar
o /var/cpanel/horde/overlay.$hordever.tar.gz
As with the prior tarballs, the value of $hordever must match what is defined in the update-horde script. The overlay tarball
provides a simple way of customizing specific aspects of Horde. For
example, certain graphics, themes, modules, plugins and the like can
all be provided as an overlay. Since it is extracted into
/usr/local/cpanel/base, the contents of the tarball must match the
directory layout found in /usr/local/cpanel/base/horde.
From this file I was able to discover the following steps to override the inline HTML view setting is as follows:
tl;dr: here are the steps:
In a temporary directory, create the horde/imp/config/mime_drivers.d/ directory structure which cPanel expects:
mkdir -p /tmp/horde/imp/config/mime_drivers.d
Create an override file in that new directory. I named mine html.php but you can name it anything you like as long as it ends in .php
Insert the following contents into /tmp/horde/imp/config/mime_drivers.d/html.php:
<?php
/**
* HTML driver settings
*/
$mime_drivers['imp']['html'] = array(
'inline' => true,
'handles' => array(
'text/html'
),
'icons' => array(
'default' => 'html.png'
),
/* If you don't want to display the link to open the HTML content in a
* separate window, set the following to false. */
'external' => true,
/* Run 'tidy' on all HTML output? This requires at least version 2.0 of the
* PECL 'tidy' extension to be installed on your system. */
'tidy' => false,
/* Check for phishing exploits? */
'phishing_check' => true
);
Create a .tar.gz version of the /tmp/horde directory at /var/cpanel/horde/overlay.tar.gz:
cd /tmp
tar -czvf /var/cpanel/horde/overlay.tar.gz horde
This file should be expanded by cPanel every time Horde is updated, re-adding your configuration override.
Move the /tmp/horde/imp/config/mime_drivers.d/ into place:
mv /tmp/horde/imp/config/mime_drivers.d /usr/local/cpanel/base/horde/imp/config/
Log in to Horde to test.
working with a service provider's management interface, such as cPanel.