Normal Thunderbird still gets two to three dozen email subject lines on the screen. I absolutely love it, I've been using it for over 20 years through the rough and through the good. We're in a good period now, and it's been a good period for quite some time.
I was impressed that it correctly inferred the IMAP and SMTP settings for my custom domain name, but after using it for ~30 seconds random old emails started appearing at the top of the email list, above my latest emails.
Maybe I'll try again in another 5 years.
edit: someone thinks i didn't wait for imap to finish. I did. My latest email appeared at the top. Then 30 seconds later some ancient emails popped up above it, seemingly triggered by scrolling in the email list pane.
That's beyond just breaking "Have sensible defaults", and is well into, "Your defaults are broken".
But it sounds like OPs mails were sorted differently for an unknown reason.
Also, which use-cases do you have where you need to see 20 emails at once?
[^1]: https://www.pixelbeat.org/docs/netscape_email/ns_4_email.jpg
And I’m sorry, you really can’t fathom why someone who gets a ton of email would want to see more of them in their inbox at the same time?
Look at the Thunderbird 1 and 3 screenshots on that page
And Netscape in 1995 look good in comparison to.. Pine?
Netscape 2.02 or Microsoft Mail client from back then looks amazing by comparison.