[exim] Question about forwarding full email addresses from /…

I'm trying to add /etc/aliases processing for simple forwarding
for virtual users to Ubuntu's default configuration.

For example, for a host with 100s of domains, forward
some virtual user to gmail...

    foo@???: doda@???

Seems like this should be simple as matching an address then
rewriting all the headers + forwarding it on... something like this...
which is incorrect....

forward_virtual_user:
driver = redirect
data = ${lookup{$local_part@$domain}lsearch{/etc/aliases} {$value} fail} bctfrF

This seems to be working, except headers never get rewritten.

Any suggestions about the best way to forward pure virtual users
to an external email address?

Thanks.