[Osiris]

Mails are sorted chronologically in Thunderbird by default but they are not grouped. Grouped means special folders for mails that arrived today, yesterday, last week, two weeks ago and old mail. This way of sorting mails is incredibly helpful for a better overview in my opinion.
You can enable that view by clicking on View > Sort By > Group By Sort G. Every mail that you have received will be sorted into one of the five special folders mentioned above. Found this little tip at mmynews, a German tech related blog. Take a look at the screenshot to see how this looks in Thunderbird

The view menu offers several other ways to display mails in Thunderbird. You can enable a threaded view for instance or sort the mails by another variable than date. Possible variables include Sender, Subject, Tags and Priority.

Group Mails in Thunderbird chronologically