@WalterH Thanks for pointing that out.
Updated my test server this morning. Works so far, I'll have another round of tests just to make sure.
Btw, my "historical" server worked well for the EX form rules probably because in /etc/gromox/gromox.cfg I had x500_org_name=iXXXXXXXX which I don't have in my new test installation (vanilla one, just the appliance and updates).
Anyway, I'll have some more tests before switching my historical server.
Glad this could get sorted out.