We're running the 5.0.8 NE Professional for reference. I've begun to run into the issue where NDR backscatter is to the volume that it gets us placed on blacklists. Looking at the Postfix config and the forum I found that smtpd_reject_unlisted_recipient is turned off by default. However after enabling the option and both reloading Postfix and restarting the full suite, it still isn't working as intended. Here's an example after having enabled the option:

Code:
Nov 18 16:00:56 mail postfix/smtpd[28210]: B5D995D70032: client=unwired.iowalab.com[192.168.xxx.xxx], sasl_method=PLAIN, sasl_username=xxxxx
Nov 18 16:00:56 mail postfix/cleanup[30184]: B5D995D70032: message-id=<476513E7-2254-4A5F-B774-B5828B43ED5F@wiredrive.com>
Nov 18 16:00:56 mail postfix/qmgr[27031]: B5D995D70032: from=<xxxxx@wiredrive.com>, size=2179, nrcpt=1 (queue active)
Nov 18 16:00:56 mail postfix/smtp[4238]: B5D995D70032: to=<guh@mail.iowalab.com>, orig_to=<guh@iowalab.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=0.19, delays=0.01/0/0/0.18, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as E1D8D5D7004F)
Nov 18 16:00:56 mail postfix/qmgr[27031]: B5D995D70032: removed

Nov 18 16:00:56 mail postfix/smtpd[30206]: E1D8D5D7004F: client=localhost.localdomain[127.0.0.1]
Nov 18 16:00:56 mail postfix/cleanup[30183]: E1D8D5D7004F: message-id=<476513E7-2254-4A5F-B774-B5828B43ED5F@wiredrive.com>
Nov 18 16:00:56 mail postfix/qmgr[27031]: E1D8D5D7004F: from=<xxxxx@wiredrive.com>, size=2766, nrcpt=1 (queue active)
Nov 18 16:00:56 mail postfix/error[705]: E1D8D5D7004F: to=<guh@mail.iowalab.com>, relay=none, delay=0.01, delays=0/0/0/0, dsn=5.0.0, status=bounced (mail.iowalab.com)
Nov 18 16:00:56 mail postfix/bounce[4249]: E1D8D5D7004F: sender non-delivery notification: E392F5D70051
Nov 18 16:00:56 mail postfix/qmgr[27031]: E1D8D5D7004F: removed
Despite the setting in Postfix to reject on an unknown user ('guh' in this case) what appears to be happening is that the message is accepted anyway and then handed off to a second queue running on the localhost IP, which determines the user is non-existent and bounces back the NDR. Is there a known fix for this situation, or am I to just make a catchall and blackhole all invalids?