Mozilla WebMail

Útil para quem usa contas Yahoo! Mail e Hotmail:

The Web-Mail extension creates a platform which other extensions use to integrate web based email accounts into Mozilla Thunderbird. POP is the only protocol supported, this means Thunderbird can only download emails. To send emails use your ISP’s SMTP server, Thunderbird will set the “Return-Path” and “From” email headers using the web account email address, too the recipient the email will appear to have come from the web base account. Currently only Hotmail, Yahoo, and Lycos accounts are supported.

(só não percebo a razão de apenas providenciarem POP... :-S)