using Thunderbird email on iCloud acct moved from MobileMe
Apple has a KBase article about configuring other mail apps, such as Thunderbird, to use iCloud iMap email:
http://support.apple.com/kb/HT4864
I found that there are two outright errors in this and one tip that you might have to do to make things work in Thunderbird.
First, after moving from MobileMe to iCloud, change your password. Even if your old password met the criteria of at least 8 characters, one number, and one Capital letter, change it anyway. This will perform a soft reset on your email account. Without this reset, many old accounts won't work with Thunderbird, even if they work fine with Apple Mail on Lion.
Then the KB instructions below have to be changed slightly, see bold:
IMAP (Incoming Mail Server) information:
Server name: imap.mail.me.com
SSL Required: Yes Connection Security: SSL/TLS Authentication: Normal Password
Port: 993
Username: example@me.com (use your @me.com address from your iCloud account) Don't use the @me.com part here!
Password: Your iCloud password
SMTP (outgoing mail server) information:
Server name: smtp.mail.me.com
SSL Required: Yes
Port: 587
SMTP Authentication Required: Yes Authentication Method: Normal password / Connection Security: STARTTLS
Username: example@me.com (use your @me.com address from your iCloud account)
Password: Your iCloud password