[Exim] explicit routing with exim -bm

My program wants to send an email, so it invokes 'exim -bm'. It wants
the message to go through a relay out in the network and come back to
the same system on which the program is running. (Its purpose is to
test the network). So it uses a recipient address as follows:

exim -bm @[206.63.251.121]:bryanh@???

and then supplies the message on Standard Input. This works fine with
'sendmail' in place of 'exim'.

But with Exim, Exim just delivers the mail directly (I'm running the
program on giraffe-data.com). It ignores my explicit routing. Is
there something I may have misconfigured to produce this result? How
can I explicitly route my message through a relay?

--
Bryan Henderson                                    Phone 408-621-2000
San Jose, California