If you have any issue while viewing html codes in Horde mail, you can fix the issue by using the following steps.
We need to change the configuration files /usr/local/cpanel/base/horde/imp/config/mime_drivers.php and
mime_drivers.php.dist . The line we have to change is:
$mime_drivers['imp']['html'] = array(
'inline' => false,
To
$mime_drivers['imp']['html'] = array(
'inline' => true,
