Public Folder and sharing calenders

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I have installed Exchange Server 2003 for a small Department. How is
the public folder and
sharing calenders implemented for small departments?
Can users in AD share documents and modify documents instead of e-mails
going back and forth?
Can all users have centralized e-mail addresses and also should have
their own e-mail address list.
Also able to see each others Calender to setup meetings?
thanks

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