e-mail server for intranet

[Yagnesh Desai]

Dear Joris and Matthew;

Thanks for your very prompt reply.

Very sorry for my ignorance and language which
confused me and you both.

Firstly :
So I need a mail server which is able to communicate
with mail clients using "IMAP", while as a mail client
any client which supports IMAP (which most of them do)
will work.

Though my preference is to also have web browser based
mail access for the users (something like gmail/yahoomail).
I think some available php modules would do the trick.

Secondly :
I need to put ristriction on SMTP communications
so that the mail server only communicate with other two
mail servers in intranet and no other server.

So what are the recommendations here.

Consider me as a novice here who want this thing working
where this will be only linux installation while all the
other servers and desktops are M$.
Yagnesh