e-mail server for intranet

[Yagnesh Desai]

Friends;

I want to start a e-mail service in the intranet.
It will be closed message service with attachment.

I find that IMAP is what i need and I will also
need a php web client for users of linux and windows
desktop to use it via web browser.

I specifically do not want the smtp support for this
mail users.

Now my specific requirement is that there are already
running Novell Groupwise and Lotus Notes mail services
in this intranet which are having 2 different domains.

The new email server which I introduce in the internet
should be able to send and receive mails to these 2
domains (not via SMTP).

I found Courier IMAP and Cyrus IMAP.
Firstly what should be my choice for the IMAP server
and the php.

Thanks in advance.
Yagnesh.