To enable horde from the plesk panel, follow these steps.
1. Login to Plesk control panel.
l.
2) Click the "Domains" shortcut in the navigation panel.
3) Click the required domain name in the list.
4) Click on Mail Accounts > Mail Settings.
5) Select the dropdown menu for Webmail and select the client "Horde"
for webmail.Click on "OK" button at the bottom right on the panel once
you have selected the "Horde" client.