While accessing an email using Horde, you may notice that Horde isn’t displaying the contents of the email rather it displays the following message
"there are no parts that can be displayed inline."
The reason is the “inline” setting of the HTML driver is set to false. To fix the issue, you need to enable i.e. change false to true for “imp/html/inline” attribute in the Horde’s mime_drivers.php file.
$mime_drivers['imp']['html'] = array( 'inline' => false;
On a Plesk server, the file is located at /etc/psa-horde/imp/mime_drivers.php and the attribute is as:
$mime_drivers['imp']['html']['inline'] = false;
Once you change the attribute to ‘true’, save the file and Horde will start displaying the contents of the email.