I tried to set up some forwading/filtering from Usermin using the "Filter and Forward Mail" module, but encountered the following message.

Warning - The system is configured to not process user-defined mail filters. Any filters defined below are unlikely to work.

I continued anyway and forwarding of email worked, but auto-replies did not. I had the same results using the "Mail Forwarding and Replies" module. Did I miss something somewhere to allow users to define their own filters?

I am using Virtualmin Pro 3.48.

Ok, my issues were caused by misconfigured DNS. The mail was being created, but not being sent because Postfix couldn't resolve the destination domain. I can't explain why the forwarding was working before although it shouldn't have been. DNS is fixed and they're both working now.

I decided to stick with the "Mail Forwarding and Replies" module instead of the "Filter and Forward Mail" module because I preferred its simpler interface so the warning mentioned above does not affect me as it does not appear in the "Mail Forwarding and Replies" module.