[ Thanks to lauren for this link. ]
“5 Open Source Microsoft Exchange Killers: Ubuntu Server
“The popular Ubuntu Linux, famous for its polished, easy-to-use
desktop version, also has a specialized Ubuntu server edition. This
is more than a re-packaged Ubuntu Desktop; it comes with a kernel
tuned for server duties, a full complement of server software and
no graphical interface. This is a serious, lean mean server
operating system.“Ubuntu Server does little handholding, so it’s not for novice
system administrators. Rather, it is for the experienced sysadmin
who wants maximum control. It includes a number of enterprise-ready
features such as AppArmor for security, private cloud, public
cloud, high availability, a Landscape client for systems
management, Mac OS X and Microsoft network integration, and
virtualization.“The installer serves up a number of useful package groups such
as Virtual machine host, Samba file server, LAMP stack, Printer
server, and Mail server. The Mail server group installs Postfix
(SMTP), and the excellent Dovecot for POP3 and IMAP4, which is a
stout foundation for an on-site email server. Then add whatever
additional services you want, such as a Webmail server,
calendaring, shared contacts, discussion boards, file shares, and
so on. Or you can install a prefab groupware suite on it.“Ubuntu Server is free of cost, and various commercial support
and systems management options are available.”