Problematic grouping of conversations by subject line

Hi, I’ve just come back to try eM Client again (v9 this time) and one thing I notice is that conversations seem to be grouped by subject line, so that I (as a web developer) have many people emailing me with generic subjects such as “website”, and these are being grouped together in a single conversation when they are not related.

Is it possible to get it to check on a combination of subject and sender/recipient?

I have one conversation containing 384 emails from dozens of people because they all have a blank subject line, which is not useful.