Synchronizing webmail folders with Thunderbird

Hi there
I am in the process of switching ISPs. My wife has an email address with the old ISP that she has always managed through the ISPs webmail interface. She has thousands of emails at that account organized into various folders. In order to have an archive of all sent and received messages from that account I am going to install Thunderbird on her computer. I think that the first time I log into the account via Thunderbird it should download all of the received emails from the server. Is this correct? Even if she has created various subfolders? Should I expect it to download all sent messages too?
Thanks for any help.
K

Thunderbird should download all of the received messages. You may want to consider creating the proper folders in Thunderbird and setting up rules to move the received e-mails to the proper folders first. Also, you may want to also make sure that you specify to leave the e-mail on the server, in case something goes wrong. That way you can always try again. I don't know about the sent e-mails being automatically downloaded. You may have to move them to the received mail folder (or a subfolder of the received mail folder) in order to get them to download.