Name: Your Name (Whatever you want)
Email: xxxx@16mail.com
Password: Your 16mail.com account password
Description: 16mail.com
Click Next Button
Hostname: imap.fastmail.com
Username: xxxx@16mail.com
Password: Your 16mail.com account password
Hostname: smtp.fastmail.com
Username: xxxx@16mail.com
Password: Your 16mail.com account password
Click Save Button
Use SSL: Yes
Authentication: Password
Server Port: 993
Use SSL: Yes
Authentication: Password
Server Port: 587