[Exim] Rewriting ( i assume?)

(Exim 4.12)
Trying to get Sympa to work nice with a few generic
routers/transports.... But one thing has me a bit baffled.

Suppose I get a incoming message for sm7h-lista-owner@???
Then I need to pipe driver which has a different address, something
like.

command = "/home/sympa/bin/bouncequeue sm7h-lista@???"

is this where I should use a local_part_suffix?