How to enable HTML emails for webmail (Horde/IMP)

Edit the file /home/httpd/html/horde/imp/config/mime_drivers.php to enable inline support for the mime types you wish to have displayed inline. Simply set the 'inline' array element for that mime type to 'true' to enable a type. As noted above, not all mime types can be shown inline; if there is no 'inline' array element for a mime type than that type can not be viewed inline.

For example, to enable inline html support you would set:

$mime_drivers['imp']['html']['inline'] = true;