Enabling Inline HTML Viewing in Horde
To display HTML messages in-line, it may require a configuration
adjustment to Horde, as noted by the Horde IMP "INSTALL" documentation.
* By default, IMP is configured to NOT display text/html message parts
inline. This is done for various security reasons. If you would like to
see text/html parts inline, you must make this change in
horde/config/mime_drivers.php and horde/imp/config/mime_drivers.php:
$mime_drivers['imp']['html']['inline'] = true;