Hello,
My server is mandriva 2005.
eth0 is WAN with static IP
eth1 is LAN.

I would like to run a postfix mail server.

By default the install is :

postfix-2.1.5

I have further on the CDs :

cyrus-imapd
cyrus-imap-utils
imap-2004c1

Or shall I use :

courier-imap
courier-imap-pop

As I see in many tutorials.
If yes what is difference.

I would also like to integrate clamAV

Any link to a postfix help is most welcome.

Thanks in advance

Varun

See the link in my sig below for Postfix/Spamassassin setup. It got my postfix servers up and running.
I don't know what the difference is with the packages you listed, but I imagine which ones you need depend on the type of mail server you are setting up. Google each one of them by name and look at their descriptions to see if they needed for your system. Additionally, if administering postfix is something you will be doing a fair amount of, I highly suggest the O'Reilly book Postfix. I can't emphasise enough how cool that book was to have around.