Email loop with other service provider

[Mari Vallius]

We have a subcontractor (with Servicenow) and we should get notifications from their system to ours, but somehow prevent our system not to send back to them our automatic responses. And jira is currently lacking that you could block the automatic replies to specific addresses.
So how to handle this. We want to have emails from their system, but not respond to them?
Their emails are now rejected by Bulk email handler, but if I whitelist/allowlist the address, we respond back and that opens tickets in their system.

ideas?