Can I access my Netscape WebMail or Hotmail accounts through Thunderbird?
No. Netscape WebMail and Hotmail use proprietary protocols. To access WebMail directly through an e-mail client requires you to use Netscape 6+ with AIM; to do so with Hotmail requires either Microsoft Outlook or Outlook Express. There are also freeware applications available that will let you do the same thing, such as Hotmail Popper.
Another example is Gotmail, which is a utility to non-interactively download email from a Hotmail account. It can download messages from all folders, messages from certain folders, or new messages only. There are options to delete downloaded messages or mark them as read. Gotmail can forward messages to other email addresses or save them as local mbox-style mailboxes.