WebTop sorting only sorts left of domain?

I just noticed and couldn’t believe it.
This can even classify as a bug, not just a limitation!
I wanted to clean up a low usage account, so I sorted by sender, even grouped by sender, only to realize that the grouping was weird. A few from some sender, a few from another, a few from the first, one from some third… Then I realized WebTop only sorts LEFT of @. So all “newsletter” for example from 10 different companies, are “together” (yet grouped split in small packs).

This is definitely wrong.

It should sort based on COMPLETE email (inc. domain) and even (for sender) then sort by claimed name of sender (after sorting by email).