postfix as satellite or null client or mua only (send email thru other server)

[Jeff Sherk Forerunner Ministries]

Ok, I have been reading and googling for two days now (docs on this site, centos.org, and lots of other sites as well), and I just cannot figure out how to accomplish making postfix (on one server, let's call it centos-server) connect to my mail server (another server, let's call it mail-server) and use this mail-server to send the email... basically need postfix to act like a send-only MUA like Outlook, Thunderbird, etc. (just connect, send the email, and disconnect). My mail-server is fully functioning and I can send emails, for example, from Thunderbird using Username: myem...@mydomain.com and Password: mypassword. This seems to be a rare way to setup postfix, so the examples just don't seem to cover what I am trying to do: I do not want to receive any email on the centos-server with postfix. I do not want to deliver any email locally on the centos-server with postfix. I do not want to relay any email thru the centos-server with postfix. I do not want to send email directly from the the centos-server with postfix. I DO want to send email from the centos-server by securely connecting to mail-server (with username and password) and then let mail-server worry about how to send the emails. I believe this has something to do with SMTP (but not SMTPD), and maybe SASL and possibly the Aliases file as well, but I just cannot figure it out! The biggest problem I am facing (at the moment) is I don't understand how to set up smtp properly in postfix (on the centos-server) so that it will provide the Username and Password for authentication. Where do I put these credentials, and how do I tell postfix to use them when trying to connect to the mail-server! Using CentOS 5.5. Ran yum update Sendmail is not installed. Postfix is installed (and running). ANY help appreciated. Thanks