thunderbird-ice

If the window Welcome to Thunderbird opens when you start Thunderbird for the first time, then choose I think I'll configure my account later.

→ Click the Alt key on your keyboard to see the the menu row on top of the window.
→ Choose Tools and Account Settings. → Click Account Actions and choose Add Mail Account.
Your name: Is the name you want the receiver to see as sender.
Email address: Your email address.
Password: Your email address password.
Remember password You probably want Thunderbird to remember the password.
→ Click Continue and choose Manual config.

Incoming: should be IMAP.
Server hostname is mail.1984.is
Port 993 SSL/TLS
Authentication Normal password.

Outgoing: SMTP
Server hostname is mail.1984.is
Port 587 STARTTLS
Authentication Normal password.
Username: Incoming: Your email address, Outgoing: Your email address.
→ Click Done (or Re-test).