Clients connecting to the Message Submission port must be authenticated. It must not be allowed that anyone on the internet could send mails through the server, because spammers quickly find such an open-proxy SMTP server and starts to use it.
Authentication is based on either the name-password pair of a user account, or on the IP address of the client. For remote users with dynamic IP addresses the password authentication, for servers the IP address based authentication is the more useful.
submission/authorized-ip.js and insert the IP addresses or address ranges,
from which machines are allowed to send mail without password authentication.
For example if your private network is 192.168.0.0/24 and you allow machines on
your private network to send mail without password authentication,
insert the following line:
... "192.168.0.0/24", ...