Compatible Operating Systems:
Linux:
CentOS 7.x
CentOS 6.x
CentOS 5.x
CloudLinux 6.x
CloudLinux 5.x
Debian 7.0
Debian 6.0
openSUSE 13.1
openSUSE 12.3 (EOL: September 15, 2014)
RedHat Enterprise Linux 7.x
RedHat Enterprise Linux 6.x
RedHat Enterprise Linux 5.x
Ubuntu 14.04 Server LTS
Ubuntu 12.04 Server LTS
Ubuntu 10.04 Server LTS (EOL: April 1, 2015)
Windows:
Windows Server 2008 R2 SP1 (EOL: January 13, 2017)
Windows Server 2008 SP2 (EOL: January 13, 2017)
Windows Server 2012 R2
Windows Server 2016
BOLD = Indicates a Parallels-recommended operating system
EOL = Indicates the OS is at End of Life for support and will not be available for use in future revisions.

Incompatible Operating Systems:
Fedora
Debian GNU/Linux 4
openSUSE 10.3
openSUSE 11.0
openSUSE 11.1
Hardware Requirements
For Linux:
512 MB of RAM (1 GB when hosting many accounts; 768 MB minimum when also using Web Presence Builder)
10 GB Hard Disk
For Windows:
1 GB of RAM (2 GB when hosting many accounts to allow for a reasonable amount of swap space*)
32 GB Hard Disk
Supported Browsers
Firefox 30.0 and above
Microsoft Internet Explorer 8, 9, 10
Safari 7.0 and above
Google Chrome 35.0 and above
Mail Client Requirements
Any mail client supporting SMTP, POP, or IMAP. Plesk documentation describes setting up MS Outlook, MS Outlook Express, Apple Mail, and Mozilla Thunderbird to work with Plesk mail.

Supported Mail Servers
Qmail 1.03
Postfix 2.6-2.9
MailEnable Standard/Professional/Enterprise 5.10-8.5
SmarterMail 6.8-12.0
IceWarp Mail Server 10.0-10.4.5