[exim] Forwarding ALL local e-mail to a specific external us…

Hello,

My setup is Debian Etch with exim4 configured as "mail sent by smarthost;
receive via SMTP or fetchmail" with Gmail as the smart host.

The machine does NOT receive any incoming SMTP (listens only on 127.0.0.1,
behind a firewall on a dynamic IP address.

I'd like to configure it so mail sent to any unqualified user name (e.g.
"amos" or "root") will get forwarded to my gmail.com account.

I tried using "/etc/aliases" to do that but it appears that exim will only
update the envelope but the message it generates still causes gmail.com to
try to deliver the message to "amos@???" (or "amos@" if
/etc/mailname is empty).

Digging the manuals and the net so far haven't come up with anything.

I'm sure this is possible but would appreciate a pointer to an explanation
on how to achieve this.

Thanks,

--Amos