Most server oriented Linux distribution consists of a bare system with manual configuration of every single services and no integration. THose are provided as a product, not as a solution.
I'm using SME Server 7.3, a nice CentOS based distribution, wich provide a large set of features, including (from contribs.org website) :
Ease of Administration
... web-based interface to enable easy administration ...
File and Print Sharing
... easy sharing of files and printers to Windows and Macintosh clients... via web, ftp, or file sharing.
... gateway ... minimal configuration...
... secure reliable email server ... individual and group addresses... webmail ... Antivirus and SpamAssassin ...
... client-to-server VPNs...
Raid and Backup
SME use a template based configuration system writent in perl. It's a real pain to customize some configuration files, but in most case it just works.
SME server is currently a good alternative to Windows SBS server and is up and running in less than 30 minutes in most cases.