Setting up email
How would I go about doing the following:

I need to setup the email with some authentication relay to another email server. In this case, I will be using one of my public email addresses and it's email server and I will probably use username/password authentication. I may have to change the port on which "sendmail" is run because some ISPs block this information.

On the Ubunto system that I have created, I need to configure the server to have the capability to send email to the internet. I may need to relay email through a valid email server using username/password authentication.

I need to install postfix on the system
app-get install postfix (hint)

I need to install Mail (mailx) on the system

I need also need to setup root's email as follows

A copy should remain local on the machine

A copy should be sent to one of your public email addresses

I need to get the public email working first.

Any help would be appreciated,