Plesk manages the work of web, mail, DNS, and other services. Technically, Plesk does not provide the services by itself; it just takes control over a number of third-party components. For example, when a customer creates a website through the Plesk GUI, Plesk propagates this request to a web server (Apache or IIS) and the latter adds a new virtual host to the system. The list of components is defined during Plesk installation (see the Deployment Guide for details). Plesk allows you to view the list of installed components, add new ones, switch between interchangeable components, and remove them (only in Windows).

Viewing Plesk Components

You can view the list of installed components and their versions in Tools & Settings > Server Components. Plesk for Windows has an additional indication of a component state (the appearance of the icons depends on the Plesk theme):

• means that Plesk is using this component, and the component is working.
• means that Plesk is not using this component (usually because a license key has expired or missing), but the component is working.
• means that Plesk is not using this component because the component is stopped.
• means that Plesk is not using this component, but the component is installed on the system and is available.

Installing Plesk Components

If you did not include a component in your Plesk installation, you can add it later in Tools & Settings > Updates and Upgrades > Add Components.

Switching Between Interchangeable Components

Some Plesk components are interchangeable. For example, in Windows you can use either MS DNS Server or BIND as your DNS server; in Linux you can choose between Postfix and Qmail for mail delivery, and so on.

On Plesk for Linux, you can switch between interchangeable components in two ways:

• Using service settings. Some Plesk components with a similar purpose can be installed side-by-side on the same Plesk server. For example, if you have two installed antivirus components, you can specify the one that will process your mail in Tools & Settings > Mail Server Settings.
• Using Plesk Installer. Some Plesk components with a similar purpose do not allow side-by-side installation. For example, there can be only one mail server in Plesk: either Postfix or Qmail. In this case, you should choose the component you want in Tools & Settings > Updates and Upgrades > Add Components.

On Plesk for Windows, you can switch between interchangeable components in Tools & Settings > Server Components. To perform the switch, click on the component name (for example, Mail Server) and select the required component from the list.

Removing Plesk Components (Windows)

If you no longer need a certain Plesk component, you can remove it from Plesk in Tools & Settings > Updates and Upgrades > Add/Remove Components or by clicking the Add or Remove Components link on the Home page.