If an incoming email is opened in a text editor, you can see it has a "Received" date and time field (usually on line 2 or 3) and much further down it shows a "Date" date and time. "Received is the time its delivered to the inbox, "Date" is the time the sender sent it. In most cases these times are very close, maybe a second or two different. But in some cases, especially with mass emails, the Date and Received times can be quite different. The recent example was 1.5 hrs difference.
Thunderbird uses the "Date" date/time whereas most other email apps I've tried use the "Received" date/time. I'm less concerned when a person pushed the send, I'm more interested in when I actually got the email.
I hoped the "sort by" could use "Received" because that's one of the options, but it does not use that, and I see no difference between sorting by "Date" or by "Received".
An option in settings or on a menu to show emails by either Date or Received would be excellent.