How-To Create/Edit Local Config Files (.local.php) this is a new page and work is in progress, if you have anything to add please update First read Configuration Files Applying changes to the files in config/ (does not apply to conf.php as this is managed though the web-interface and updated automatically) directories is not recommended as when you update Horde modules these files will be replaced. Horde has supplied us a method to get around this problem with local overrides which are not overwritten each time the modules are updated. There are also other methods such as vhosts or prefs.d/ which this article does not go into directly but the principle is the same. There are a few ways to add entries into the local files. Replace full array $mime_drivers = array( /* HTML driver settings */ 'html' => array( /* NOTE: Inline HTML display is turned OFF by default. */ 'inline' => false, 'handles' => array( 'text/html' ), 'icons' => array( 'default' => 'html.png' ), /* If you want to limit the display of message data inline for large * messages, set the maximum size of the displayed message here (in * bytes). If exceeded, the user will only be able to download the * part. Set to 0 to disable this check. */ 'limit_inline_size' => 1048576, /* Check for phishing exploits? */ 'phishing_check' => true ) ); Replace individual array entry /* HTML driver settings */ $mime_drivers['html'] = array( /* NOTE: Inline HTML display is turned OFF by default. */ 'inline' => false, 'handles' => array( 'text/html' ), 'icons' => array( 'default' => 'html.png' ), /* If you want to limit the display of message data inline for large * messages, set the maximum size of the displayed message here (in * bytes). If exceeded, the user will only be able to download the * part. Set to 0 to disable this check. */ 'limit_inline_size' => 1048576, /* Check for phishing exploits? */ 'phishing_check' => true ); Modify individual entries within the array $mime_drivers['html']['inline']=true; Merge array to existing array (useful in the case of the format seen in mime_drivers.php) $mime_drivers=array_merge($mime_drivers,array( /* Plain text viewer. */ 'plain' => array( 'inline' => true, 'handles' => array( 'application/pgp', 'text/plain', 'text/rfc822-headers' ), /* If you want to limit the display of message data inline for large * messages, set the maximum size of the displayed message here (in * bytes). If exceeded, the user will only be able to download the * part. Set to 0 to disable this check. */ 'limit_inline_size' => 1048576, /* If you want to scan ALL incoming text/plain messages for UUencoded * data, set the following to true. This is very performance intensive * and can take a long time for large messages. It is not recommended * (as UUencoded data is rare these days) and is disabled by * default. */ 'uudecode' => false ), /* HTML driver settings */ 'html' => array( /* NOTE: Inline HTML display is turned OFF by default. */ 'inline' => false, 'handles' => array( 'text/html' ), 'icons' => array( 'default' => 'html.png' ), /* If you want to limit the display of message data inline for large * messages, set the maximum size of the displayed message here (in * bytes). If exceeded, the user will only be able to download the * part. Set to 0 to disable this check. */ 'limit_inline_size' => 1048576, /* Check for phishing exploits? */ 'phishing_check' => true ) ));