Stalwart behind inbound mail relay

[P-Froggy]

I am trying to set up Stalwart as a replacement for our old Microsoft Exchange server.
Stalwart runs behind an email archiving solution which receives email from the web via SMTP, does the archiving and spam filtering and then sends the email to Stalwart's SMTP port.
For outbound email it works the same way, just in reverse. Here everything works as expected, I just set up the archiving server as a smarthost.

However, I'm having some problems with incoming emails: Since all mails are received from the archiving server (and thus from a single IP address), the archiving server is considered a spammer and its IP address was blocked first. I worked around this by disabling the default sender throttling rule in the settings, but most emails still go directly to the junk folder when received.
In addition to the above, I have also whitelisted the IP address of the archiving server, unfortunately to no avail.

I also recently had to downgrade to version 0.9.1 because Stalwart from version 0.9.2 or higher blocks all incoming connections from the archiving server's IP address.

I would be grateful if someone could show me what settings I need to make for this setup behind a mail relay.

[mdecimus]

If you already have a SPAM filter running in front of Stalwart you should disable the built-in one by removing the script at the SMTP DATA stage.

Regarding the IP address being blocked you can add it to the IP allow list.