My sincere thanks, Viktor.
Removing the domain from $mydestination fixed the problem.
Testuser2's message was properly delivered to the mailbox on the MDA server.
-----Original Message-----
From: <owner-postfix-us...@postfix.org> on behalf of Viktor Dukhovni
<postfix-us...@dukhovni.org>
Reply-To: "postfix-users@postfix.org" <postfix-users@postfix.org>
Date: Friday, August 6, 2021 at 11:04
To: "postfix-users@postfix.org" <postfix-users@postfix.org>
Subject: Re: [EXTERNAL] Re: Inbound/Outbound Settings on a Postfix Relay-Only
On Fri, Aug 06, 2021 at 12:33:22PM +0000, White, Daniel E.
(GSFC-770.0)[NICS] wrote:
From which we can conlude that you've listed the domain in
"mydestination" (domains delivered to local accounts on the MTA host),
which requires that the recipient "testuser2" be listed in /etc/passwd,
or in the local aliases(5) table.
Viktor.
