It seems to take almost 1 second per 10 messages to apply a rule, for some reason? I have a massively powerful machine, 11th gen i7, 32GB memory, Gen4 NVMe… there is no good reason that applying a rule would take so long?
Not sure if I am going about this wrong? Windows is showing basically 0% CPU and disk usage when eM is running the task.
Can you display a screenshot of the actual rule?
Can I assume you are talking about processing incoming mail?
That will be a one-time event if you are applying the Rule manually to existing messages.
Otherwise Rules only apply automatically to new unread messages as they arrive in your Inbox. So unless you are receiving 300k message a minute, there will be no problem.