RoundCube Autoresponder Plugin configuration

Hi folks.

We're looking at the roundcube autoresponder plugin

(https://github.com/bhuisgen/rc-vacation/)

configuration as a method of providing a bit more flexibility to users. It looks like it's compatible with maildrop. In the process of trying to set it up, we encountered this configuration option:

<snip>
// forward filename
$rcmail_config['vacation_forward_file'] = '.forward';
</snip>

Which got us to looking at how interworx handles forwarding email addresses. We are used to stuff like this being handled in a .qmail-username file, but that is not the case in interworx.

So, this may seem like a silly question, but where on the filesystem are copyto/forward email destinations configured?

Thanks.