It seems to work but only sorts messages in the same folder so basically what I see as missing is that it does not show any replies to messages in a thread. To get the same functionality as Gmail I would need to move all sent emails to the same folder as the incoming email resides in.
As far as I can see, Gmail does that beautifully so a message thread in Gmail lists all related messages going back and forth.
Am I missing something or does Sogo simply not have this feature?