Well, today I started the process of moving 13 years of emails from my Outlook Express to Thunderbird ("TB"), all on my XP machine.
I installed Thunderbird on my XP machine and had it Import all settings, folders and emails from my Outlook Express. But then when I had TB start checking for new emails, it started downloading the same very old emails that are in the successful Import.
See my details at https://support.mozilla.org/en-US/questions/1233978
Any thoughts? Thanks.