Thunderbird released an option to view emails in threaded-view, just like GMail. Considering how much I already loved Thunderbird, and at the same time wanted my emails threaded, I was very excited to see this addition to Thunderbird. The only issue that came up was that new emails within a closed/minimized thread were hidden from view. You could see that your inbox had a new message, but then (by default) you would have to open up your threads to track down your email. Now there may be a better solution to this problem, but here’s what I did:
You can right-click on the column headers (Subject, From, Date, Attachments, etc.) and add a new column called “Unread”. This will show you the number of new/unread emails within the thread. Awesome!
Hope this helps!