Using a custom support address should not break allowlist/blocklist functionality

After recent contact with Zendesk support, I have been told that use of a custom email address as a "Support Address" completely breaks blocklist/allowlist functionality.

Blocklist/allowlist functionality should look at the original sender for a matching domain. 

The ticketing system uses the original sender when identifying original user and domain.

I am told that the blocklist/allowlist only uses the forwarder address, which breaks compatability with a custom support address.