Postfix advice needed, setup a remote private relay

[batfastad]

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

[uxbod]

Have a read through Postfix Configuration - Basics to familiarize yourself with the basics of the configuration file for Postfix. The key to make sure you do not end up as a open relay is mynetworks.

[batfastad]

So I can use mynetworks to list the localhosts (default) and also our static IP address. So only connections from our IP address are accepted.
That sounds ok, I just really want to make sure I get this right.

Is that all I would need to look at?
Or should I enable SMTP auth as well?

What about setting up DNS for the relay server?
I assume I need to give it actual DNS A/CNAME records... mail2.domain.com
Since mail.domain.com is already assigned to our office Exchange server.
And give that to postfix as well in the myhostname and mydomain config sections.

Finally, how do I make sure that the server doesn't receive any mail for domain.com?
Just not list it as an MX record for the domain?
The email address the newsletters are sent from is noreply@domain.com, so will all bounce backs/undeliverables be sent to our main server (mail.dealer-world.com)?

The server provider says they'll install webmin on there to make it easier to manage the settings, although I might decide against that since postfix only has the single config file.

Cheers, B

[uxbod]

Listing the localhost and your static IP address will stop it from being a open relay. If all it is doing is relaying email then it would not require a MX record.