Name: Your Name (Whatever you want)
Email: xxxx@letterboxes.org
Password: Your letterboxes.org account password
Description: letterboxes.org
Click Next Button
Hostname: imap.fastmail.com
Username: xxxx@letterboxes.org
Password: Your letterboxes.org account password
Hostname: smtp.fastmail.com
Username: xxxx@letterboxes.org
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