[bsder]

> What was the original intent of open relays? Why allow emails without authentication?

Store and forward.

Do remember that email was THE great federated protocol.

The goal of a mail server was to get your email "at least one hop" closer to your destination. And that wasn't an easy task.

Servers came online and went offline. Users logged in and out. Connections came up and went down. IP wasn't the only transit. DNS? Oh, the hosts file? Even higher things--thing DECnet and Janet.

Email was barely functional most days. Your best bet if you weren't an Internet God and weren't able to write your own super complicated sendmail.cf was to know a sysadmin at a node who had an Internet God and ask him if you could forward emails that you couldn't handle to their server.