I still need to sort this out somehow, how to bind an IP
to a domain which is what led to my current predicament.

I added, but have since commented out a new transport in
my postfix/conf/master.cf, reading:

# myclient_net unix - - n - - smtp
# -o smtp_bind_address=173.203.123.123
# -o smtp_helo_name=myclient.net
# -o syslog_name=postfix-myclient_net

In main.cf I added, but also commented out:

# sender_dependent_default_transport_maps = regexp:/opt/zimbra/postfix/conf/sdd_transport_maps.regexp

and the referenced file in this case includes:
/@myclient\.net$/ myclient_net:

In the browser interface, upon email submission, we see:
"an unknown error (mail.TRY_AGAIN) has occurred"

At ten minute intervals my /var/log/mail.log reminds me:

Oct 6 04:00:01 vodaplex postfix/postqueue[17118]:
fatal: Queue report unavailable - mail system is down

hesco@zim:/opt/zimbra$ sudo -u zimbra bin/zmcontrol restart
Host mail.vodaplex.net
Stopping stats...Done.
Stopping mta...Done.
Stopping spell...Done.
Stopping snmp...Done.
Stopping cbpolicyd...Done.
Stopping archiving...Done.
Stopping antivirus...Done.
Stopping antispam...Done.
Stopping imapproxy...Done.
Stopping memcached...Done.
Stopping mailbox...Done.
Stopping logger...Done.
Stopping zmconfigd...Done.
Stopping ldap...Done.
Host mail.myclient.net
Starting ldap...Done.
Starting zmconfigd...Done.
Starting logger...Failed.
Starting logswatch...failed.


Starting mailbox...Done.
Starting antispam...Done.
Starting antivirus...Done.
Starting snmp...Done.
Starting spell...Done.
Starting mta...Done.
Starting stats...Done.
hesco@zim:/opt/zimbra$

I'd appreciate some guidance toward restoring services and then implementing the binding of specific IP's to a domain.

Can anyone advise me please on next steps?

-- Hugh Esco