I use Thunderbird to download emails from AT&T (Yahoo) to my laptop, and I leave all messages on the server as a backup. That has worked fine for a long time.
Each time I started up TB, it only downloaded new messages, specifically the UNread messages from the Yahoo INBOX; they automatically were marked as Read at Yahoo, and UNread inside TB on my laptop.
After many many months of using Thunderbird 2, I upgraded to the new version of Thunderbird on December 8th, 2009.
Now TB wants to download ALL 16000+ messages in the AT&T/Yahoo inbox, including all the previously downloaded messages, instead of just the couple of hundred messages that are truly new.
I think that would take a long time, eat up drive space, and create thousands of duplicated messages in the TB inbox on my laptop.
HOW can I tell Thunderbird and Yahoo to cooperate once again and only download messages (to my TB inbox) that have landed in the Yahoo inbox since December 8th?
I hope I have explained the situation clearly, thanks for any insights and suggestions.