Name: Your Name (Whatever you want)
            Email: Your email address is your username
            Password: Your letterboxes.org account password
            Description: letterboxes.org
            
Click Next Button
Hostname: imap.fastmail.com
            Username: Your email address is your username
            Password: Your letterboxes.org account password
Hostname: smtp.fastmail.com
            Username: Your email address is your username
            Password: Your letterboxes.org account password
            
Click Save Button
Use SSL: Yes
            Authentication: Password
            Server Port: 993
Use SSL: Yes
            Authentication: Password
            Server Port: 587