My Thunderbird automaticaly update the addon WebMail to 1.4.5 and Yahoo 1.5.5. After i get "Thats Cool" Message :-( and can not connect to server. After downgrade to WebMail 1.4.4 everything OK. Here is link for older WebMail: http://downloads.mozdev.org/webmail/web-mail-1-4-4.xpi
Michal.
