We have a clustered setup of two servers. The admin server (henceforth called zimbra) runs the full version of Zimbra while our agent server (henceforth called zcs2) is the free-version.
The distribution group in question exists on the agent server, forwarding accounts exist on the agent server as well since the users of this particular distribution group are on the admin server.

The problem that I am seeing is the distribution group receives emails from the outside world, but internal mail sent to the distribution group are hitting a catch-all mailbox.

Email sent internally to distribution group:
root@zimbra:~# tail -300 /var/log/zimbra.log | grep "jobstatus"
Sep 18 15:30:47 zimbra postfix/smtp[4989]: B9644A630DE: to=<_catchall@mydomain.com>, orig_to=<jobstatus@mydomain.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=1.3, delays=0.02/0/0.01/1.3, dsn=2.0.0, status=sent (250 2.0.0 from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as 04CE4A630E9)
Sep 18 15:30:47 zimbra postfix/smtp[4989]: B9644A630DE: to=<_catchall@mydomain.com>, orig_to=<jobstatus@mydomain.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=1.3, delays=0.02/0/0.01/1.3, dsn=2.0.0, status=sent (250 2.0.0 from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as 04CE4A630E9)
Sep 18 15:33:23 zimbra postfix/smtp[4989]: DF1BAA630DE: to=<_catchall@mydomain.com>, orig_to=<jobstatus@mydomain.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=3.7, delays=1.7/0/0.02/2, dsn=2.0.0, status=sent (250 2.0.0 from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as CCE77A630E9)
Sep 18 15:33:23 zimbra postfix/smtp[4989]: DF1BAA630DE: to=<_catchall@mydomain.com>, orig_to=<jobstatus@mydomain.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=3.7, delays=1.7/0/0.02/2, dsn=2.0.0, status=sent (250 2.0.0 from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as CCE77A630E9)

Email that was sent from external account to distribution group:
root@zcs2:~# tail -300 /var/log/zimbra.log | grep "jobstatus@mydomain.com"
Sep 18 15:29:22 zcs2 postfix/smtp[6805]: D9C7F209455: to=recipient1@mydomain.com>, orig_to=<jobstatus@mydomain.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=0.82, delays=0.05/0/0.01/0.76, dsn=2.0.0, status=sent (250 2.0.0 from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as A3EBE209458)
Sep 18 15:29:22 zcs2 postfix/smtp[6805]: D9C7F209455: to=<recipient2@mydomain.com>, orig_to=<jobstatus@mydomain.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=0.82, delays=0.05/0/0.01/0.76, dsn=2.0.0, status=sent (250 2.0.0 from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as A3EBE209458)
Sep 18 15:29:22 zcs2 postfix/smtp[6805]: D9C7F209455: to=<recipient3@mydomain.com>, orig_to=<jobstatus@mydomain.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=0.82, delays=0.05/0/0.01/0.76, dsn=2.0.0, status=sent (250 2.0.0 from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as A3EBE209458)
Sep 18 15:29:22 zcs2 postfix/smtp[6805]: D9C7F209455: to=<recipient4@mydomain.com>, orig_to=<jobstatus@mydomain.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=0.82, delays=0.05/0/0.01/0.76, dsn=2.0.0, status=sent (250 2.0.0 from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as A3EBE209458)
Sep 18 15:29:22 zcs2 postfix/smtp[6805]: D9C7F209455: to=<recipient5@mydomain.com>, orig_to=<jobstatus@mydomain.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=0.82, delays=0.05/0/0.01/0.76, dsn=2.0.0, status=sent (250 2.0.0 from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as A3EBE209458)
Sep 18 15:29:22 zcs2 postfix/smtp[6805]: D9C7F209455: to=<recipient6@mydomain.com>, orig_to=<jobstatus@mydomain.com>, relay=127.0.0.1[127.0.0.1]:10024, delay=0.82, delays=0.05/0/0.01/0.76, dsn=2.0.0, status=sent (250 2.0.0 from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as A3EBE209458)


I mentioned briefly that there are already forwarding accounts configured for the recipients on the agent server. Would a "forwarding distribution group" that is set up at the command line (similar to the accounts) meet the functionality we're looking for?