Port filtering

Hello,

I have an NT 4.0 server. I would like to use only those ports that I really need and to block access to all others.

One solution is to enable security to TCP/IP protocol (advanced settings) for my netcard and to specify a DENY ALL policy EXCEPT some ports (TCP and UDP ports).

I am using the following services:

HTTP, HTTPS, FTP, SMTP, POP3 , IMAP, DNS.

Which TCP/UDP ports should I left open?

If you can suggest a specific policy of any other ports that should be left openplease tell me in order to avoid problems. I know that tough security might cause various problems to the operation of the Server.

I do not want to block a TCP or UDP port that might cause problems to any of the above services.

Thank you in advance.