Hi everyone

We run a small email newsletter service (3,000 subscribers strictly opt-in only, sent daily) and we're moving to an ISP that does not operate a mail relay.
I've been looking into various options and the best one for us appears to be renting a virtual private server. I have found a company and discussed this usage with them and they said it should be fine.

Basically I was looking to configure postfix as a private relay to send our newsletters through.
The server will be running CentOS 5 (I've only ever used ubuntu) and they will provide an installation of yum and webmin.

Is it possible to configure postfix as a private relay?
So we set our bulk email software (Group Mail Pro) to connect to the postfix SMTP server with a username/password, possibly with encryption as well, and send through that.

Is this possible?
Anyone have a list of postfix configuration changes I would need to make?

On our LAN we use exchange server (switching to Zimbra once v6 is out), and postfix as a local relay for our intranet DB interface with the relayhost directive.

So don't really know much about setting up access control with postfix, and getting it to send mail directly

Any comments/suggestions?

Cheers, B