I've used Thunderbird for years, but I don't use any of its spam filter stuff. Instead, I use an app called "Mailwasher" by Firetrust (
https://www.firetrust.com/products/mailwasher-pro. It retrieves email headers (subject, sender, date) for all three of my accounts and sorts it into spam or good. When I hit "process", it deletes the spam, opens Thunderbird and passes the good to it (it works with pretty much any other well-known email app like Outlook). At first, it labels everything with little buttons (s or g), but it then remembers your choice for the future. You can also designate a post as "friend" or blacklist it.
After you've used it for a few weeks, it's almost 100% accurate, so all I usually have to do is hit "process". If I ever want to see a particular spam item, I can uncheck the delete box, which passes it to Thunderbird but keeps it categorized for future posts as spam.
It has an added advantage in that it allows you to view the first few dozen lines of a post without opening it; and images and links are shown as code rather than actually displayed, which thwarts hidden, embedded "phone-home" codes that notify the sender that you received and opened the email.
It isn't free, but it allows a free trial.