[pfx] dual server configuration

Hello list!

I have set up a dual postfix configuration:  one cloud server and one 
server on-premises.  The split:

cloud-instance (metered):
- exposed to the hostile environment
- does quick/basic/low-effort filtering (blocks at the firewall IP 
ranges from which I do not expect anything of value; and does basic 
sanity checks)
- tunnels the messages to the on-premises instance

on-premises (unmetered):
- check for existence of alias / mailbox
- fancy anti-spam filtering (local AI)
- delivery to mailbox (hosted within the trusted perimeter)

It works well.  Almost all spam goes to /dev/null or equivalent. 
HOWEVER, it could do better on a specific use case:

some large senders commingle spam with ham.  the message passes the 
cloud-instance because I cannot hard-block google, microsoft, 
salesforce, etc. and they only get qualified as spam on the on-premises 
instance.  so my cloud instance gives them a 2yz while I would like to 
give them a 5yz to inform big tech that they are being abused.

Is there a way to configure the cloud instance:
- to wait for the receipt of a return code from the on-premises instance
- and to return that code to the sender?

Thanks,
Yuv


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