450 4.1.1 : User unknown in virtual mailbox table - 550 5.1.0 Address rejected

By default postfix is setup to use error code 450 4.1.1 when a user is not on the server. This gets retried a few times before the user is notified. I would like to configure it to give a plain 550 5.1.0 Address rejected message so that it is bounced back immediately. This way the user knows they either fat fingered the email address or it simply does not exist on the system.
I have looked at changing in the /etc/postfix/main.cf
unverified_recipient_reject_code = 550
unknown_virtual_mailbox_reject_code = 550
unknown_address_reject_code = 550
unverified_sender_reject_code = 550

But they still get rejected as 450 4.1.1

I realize that it helps spammers determine who is real and who is not but to delay a user hours to know their email did not send is a poor option as well.

Any ideas?

 

most likely this happens because you have soft_bounce set to yes and this makes all 550 codes to 450 regardless of any setting you may add into main.cf.
As per postfix's documentation:
soft_bounce (default: no)
Safety net to keep mail queued that would otherwise be returned to the sender. This parameter disables locally-generated bounces, changes the handling of negative responses from remote servers, content filters or plugins, and prevents the Postfix SMTP server from rejecting mail permanently by changing 5xx reply codes into 4xx. However, soft_bounce is no cure for address rewriting mistakes or mail routing mistakes.