[exim] Configure multiple domains

Hi.

My setup is a Ubuntu webserver with Exim4. On top of this two webapps on
different domains that are sending emails.
I want each domain to use their own interface on transport, and
halo_data should be set correctly as well.

After hours of searching the web I have manage to do this in
config_remote_smtp:

interface_address =
${lookup{$sender_address_domain}lsearch{/etc/exim4/interfaces}{$value}{xxx.xxx.xxx.xxx}}

interface = $interface_address
helo_data =
${lookup{$interface_address}lsearch{/etc/exim4/interfaces_reverse}}

The files interface and interfaces_reverse are lists with domain names
and ip addresses.

Interface is set correctly, but debugging reveals that the second lookup
is done with key = "". This should of course be $interface_address.
I can't figure out why the key is not set correctly...

The second problem is that I can't set sender_address from php. I have
tried to set the "Reply-To" header but it gets rewritten.
Why does it get rewritten (I have added www-data to trusted_users)?

I hope someone can help me with this.

--
Kjetil Wikestad