[newbie] Configure Postfix at home as SMTP relay?

[Heck Lennon]

Hello,

I'm helping someone with a phpBB forum application sitting on a shared host that isn't sending email as expected – no email is coming out through either PHP's mail() function or the hoster's SMTP server, with no error message.

Since it's shared and I'm not allowed to SSH to it, I can't check the server's /var/log/messages.

So… as a way to check if the application is actually connecting out to send emails, I'd like to set up a Postfix server on a Debian computer at home behind an ADSL router, to act as a relay between phpBB on the hoster's site, and my ISP's SMTP server, ie.

phpBB on hosted server → Internet → my ADSL router → home Debian computer with Postfix → back to the Internet → my ISP's SMTP server → final target SMTP server → POP3.

How would I configure Postfix's /etc/postifx/main.cf or master.cf for that purpose?

For instance, I don't know what domain name I should use ("mydomain"), since it's just a server at home on a private network (192.168.x.y)

Thanks for any help.