[exim] Customizing Email Headers

I'm really stumped on something and it's possible you can't actually do
this but I want to set the "Sender" field to something I want to
specify. However, it keeps assigning the sender as
apacheuser@???. I don't want that, I want to put a
different address there. Is that possible?

I tried this:

$headers="FROM: me@???\r\n";
$headers.="Sender: me@???\r\n";

And even:

$headers.="envelope-from: me@???\r\n";

No luck. Any help would be great!

Thanks!