Recipient address rejected: User unknown in virtual mailbox table;

I am using a multiserver setup where for some domains I am simply using the smtp server as an upstream spam filter checking for spam and viruses and passing on to an exchange server.
For many years this has worked fine. Recently I have found that to my alias addresses the postfix server is incorrectly identifying that the email mailbox doesn't exist. This doesn't happen for the main mailbox only for alias addresses and only alias addresses on the same domain.
in email routing I've tried with mx lookup off or on without change to symptoms.
If I disable the smtp server of ispconfig the mail is received fine. The exchange server having lower priority in DNS setup of mx records.
I'm using Debian buster and am on the 3.2.8p1 version of ispconfig.
Can anyone point me in the right direction please.

 

The latter under email routing and under relay domains it just has domain.tld without the @
No mailboxes no catchall address

 

Sorry under relay recipients it is @domain.tld

 

Tried to add an email alias and now the changes are not syncing.
ran server.sh in maintenance mode

Code:

/usr/local/ispconfig/server/server.sh
08.08.2022-08:11 - DEBUG [plugins.inc:155] - Calling function 'check_phpini_changes' from plugin 'webserver_plugin' raised by action 'server_plugins_loaded'.
08.08.2022-08:11 - DEBUG [server:177] - Found 2 changes, starting update process.
08.08.2022-08:11 - DEBUG [modules.inc:240] - Processed datalog_id 4477
08.08.2022-08:11 - DEBUG [modules.inc:240] - Processed datalog_id 4478
08.08.2022-08:11 - DEBUG [server:217] - Remove Lock: /usr/local/ispconfig/server/temp/.ispconfig_lock
finished server.php.

**** note I only upgraded to latest version yesterday and have this is the first change I've made

 

Code:

/usr/local/ispconfig/server/server.sh
08.08.2022-20:43 - WARNING - There is already an instance of server.php running with pid 1679.

This is on the smtp server and I guess this is the one being updated with new email alias.
I rebooted the smtp server with no success on solving this issue

 

Did you turn off debug mode after testing? And uncommented the cron job?
Following these instructions should help solving the issue: https://forum.howtoforge.com/threads/please-read-before-posting.58408/

 

th

Thanks