In cPanel, Horde does not display rich text/HTML emails by default, it only displays the plain text version. I know there is an option to display HTML emails, but I am not sure how to enable that under cPanel.

I read a lot of forum posts online saying that I need to set $mime_drivers['html']['inline']=true; in mime_drivers.php. However if I alter this file I am afraid that cPanel will overwrite it. cPanel has a tendency to overwrite files I modify.

How can I configure Horde under cPanel to display HTML emails?

  • I love how I searched Google for "cPanel Horde display HTML emails" earlier today and was unable to find the right answer. So I post a ServerFault question and now the right answer is right there on the first results page of Google. Stack Exchange FTW!
    – Josh
    Apr 6, 2012 at 1:29
  • This question appears to be off-topic because it is about working with a service provider's management interface, such as cPanel. Jan 13, 2015 at 22:22
  • 4
    @HopelessN00b This question is on topic because it is about managing the hardware or software of servers while working as a sysadmin for a service provider.
    – Josh
    Jan 13, 2015 at 22:35
  • Debatable, but regardless, people are seeing old questions like this as indicating that questions about how to $foo in $webadminpanel as being on topic, which is no longer the case. Closing them avoids giving that impression... or at least makes the excuse less valid. If you want your cPanel questions reopened anyway (not sure what good it would do you), feel welcome and even encouraged to bring it up on meta and/or flag your posts for reopening. Jan 13, 2015 at 23:07

1 Answer 1


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,


$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:

  1. The Horde installation is wiped clean (rm -rf /usr/local/cpanel/base/horde).
  2. 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:

  1. 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
  2. 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

  3. Insert the following contents into /tmp/horde/imp/config/mime_drivers.d/html.php:

     * HTML driver settings
    $mime_drivers['imp']['html'] = array(
        'inline' => true,
        'handles' => array(
        '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
  4. 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.

  5. 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/
  6. Log in to Horde to test.

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