[exim] Customizing Mail Delivery Failure Email

I was wondering if it's possible to modify/customize the default email
template that Exim uses to send mail delivery failure notifications (Mail
delivery failed: returning message to sender). And if so, how I might go
about it.

In particular I'd like to have the failed recipient address appear in the
subject line.

Any help/pointers would be greatly appreciated.

All the Best,
Eliot