Send yourself some email with the sendmail compatibility program, with the -N option set to "success":
Look in your logs for a line such as:
.... postfix/bounce: 0252E366385: sender delivery status notification: 11CEA3663CA
The delivery notification is sent to you with queue ID show (in the example, above, it is 11CEA3663CA). You will find a DNS sent to the email address from the bounce agent.
Configure the smtpd_discard_ehlo_keyword_address_maps *after* you get things working and you know what to look for.