Implement suppression list in Exim for some senders only

Question

I have an Exim router that for some senders delivers mail via a smarthost:

send_via_ses:
  driver = manualroute
  domains = ! +local_domains
  transport = ses_smtp
  route_list = * email-smtp.eu-west-1.amazonaws.com;
  senders = lsearch;/etc/exim4/ses-senders

I am required to maintain a list of recipients known to bounce, messages for which Exim should do the bounce instead of trying to send via the smarthost. If the sender is not on the senders list, mail is not delivered via the smarthost, and the message should not be bounced.

How can I implement this?