Just click on the header of the date-column, and it should sort the mails the other way round. I also prefer your preference, and I don't see why this isn't the standard setting.

I have not used Thunderbird in a few years and had forgotten this tip. Thanks a lot.

You're welcome. This is a concept in all window operating systems: if you want to arrange items in a list by a criterion, you just click the header. Works for example in Windows Explorer to sort files by name, type, or also date.