Using the Apache Commons to send email there is the following code.
HtmlEmail email = new HtmlEmail();
email.setHostName(SMTP_HOST_NAME);
email.setSmtpPort(587);
email.setAuthenticator(new DefaultAuthenticator(SMTP_AUTH_USER, SMTP_AUTH_PWD));
email.setTLS(true);
email.setBounceAddress("aaa@abc.com");
email.setMsg("Hello");
email.setFrom("bbb@abc.edu");
email.addReplyTo("bbb@abc.edu");
email.addTo("i.do.not.exist@abc.gmail.com");
email.send();
But the bounce will not work. It sends the bounce to the party that authenticated the message, which in this example is SMTP_AUTH_USER. So How can I get it to bounce properly?
Did you check with a packet sniffer what is actually going over the wire? I wouldn't be surprised if the MSA on SMPT_HOST_NAME ignores and overrides your bounce address.
You could try using the SMTP-port to the MTA and quickly check if this makes a difference.