If you use Thunderbird and want to make iCloud email work with thunderbird, but Thunderbird doesn’t authenticate with iCloud. Try the following step by step:
* In Mozilla Thunderbird, click Tools > Options > Advanced > General > Config Editor, and search for the string ‘mail.server.server’
* You should see mail.server.server#, where # = 1,2,3, etc. find the name of the account that you have as your iCloud account in Thunderbird, and record the value.
* go to mail.server.server#.authMethod and set it to 2
* In the navigation pane, right click your account, click Subscribe and update accordingly.
* If you have problem with imap.mail.me.com, you can switch to p99-imap.mail.me.com.