Thunderbird stopped working with iCloud email I had Thunderbird configured with an iCloud (me) email account and it worked fine until about two weeks ago. When I tried to send a message, it asked me for the server password. When I entered it, I got a message saying the login or password was wrong. I also had this same problem on another machine with another account. I was able to add and use a Gmail account without any problems.

My setting are:
Incoming

Protocol: IMAP
Server: imap.mail.me.com
Port: 993
SSL: SSL/TLS
Authentication: Normal password


Outgoing

Protocol: SMTP
Server: smtp.mail.me.com
Port: 587
SSL: STARTTLS
Authentication: Normal password


I got the settings from How can I configure iCloud mail in Mozilla Thunderbird?

I am able to login to both iCloud accounts through a browser.
Starting June 15, 2017, Apple requires two-factor authentication on all iCloud accounts that access their accounts non-natively. Apple’s third-party email client setup instructions have since been updated accordingly.

Native iCloud access is limited to System Preferences on macOS, the Settings app on iOS, and iCloud for Windows. All other apps, including Thunderbird and Outlook, require an app-specific password.

To enable two-factor authentication:


On an iOS device open Settings → Password &amp; Security and tap Turn On Two-Factor Authentication.
On your Mac open  → System Preferences → iCloud → Account Details → Security and click Turn On Two-Factor Authentication….


Then, login at https://id.apple.com/ and under Security → App-Specific Passwords, click Generate Password…. Enter that password into Thunderbird.

This was done to keep third-party apps from getting access to your iCloud password, thus reducing the likelihood of iCloud account breaches.