The only solution to import PST files to Roundcube webmail is to use eSoftTools Outlook PST Recovery software. By using it you can import your PST files to Roundcube webmail in a very simple process. You can also import your PST files to MBOX, EML, EMLX, MSG, HTML, vCard, Zimbra, and other files without any problem. This software supports all Windows O/S editions and also provides a free demo to the users in which you can recover up to 25 items from all the folders of your PST files.