You can install on the server a number of webmail software packages and select which of them should be available to your users. Alternately, you can redirect your users to an external webmail service. To do this, register an external webmail service address with Plesk by adding a corresponding record.
All installed webmail packages and registered external webmail services are listed in the mail settings of hosting plans and subscriptions (in the Mail section). There you can select which webmail to provision to users.
By default, Horde and RoundCube webmails are installed on Plesk for Linux, and only Horde is installed on Plesk for Windows. Additionally, Plesk for Linux supports Atmail, and Plesk for Windows supports the following webmail clients:
Important: If you offer RoundCube to your customers, keep in mind that Plesk backups do not include backups of the RoundCube database. This means that RoundCube data such as customers' calendars and contacts is not restored upon restoration of selected subscriptions or the entire server.
To register an external webmail service:
To change the properties of an external webmail record:
To make a webmail service unavailable for inclusion into hosting plans:
This works for installed webmail software packages and for links to external webmail services.
This way you can remove only links to external webmail services. Installed software packages can be removed only by means of Plesk Installer (Tools & Settings > Updates).