Wanting to know how email worked and then stumbling on it being mentioned next to the relevant RFCs was my first exposure! You could easily check pop3 mail over telnet, by sending all the commands by hand. HELO!
I then made my first email client, then an RFC later, and after browsing the web through telnet for a while, made my first web server!
I think I was the only one in the operations team who knew how to use telnet to check connections and existence of adresses on company and outside email servers. As well as other low level tools to diagnose problems with Windows PCs and servers. There just weren't any gui tools like that.
I have checked right now that Multi-User Dungeons we played in the 90s, still exist and are played. 35 years later!
Telnet or Mudnet client needed :)
I’ve just poked my schoolmate - he almost didn’t graduate because of MUD.
Telnet was among my debugging tools for web applications.
And sending an email without line editing felt much more exciting than a dedicated mail client. Just dig the remote MX, telnet to port 25 and do it by hand. Marvelous!
EHLO! You're definitely not alone on this RFC path ;-)
sending email over telnet was part of my training as tech support for a dial-up ISP.
I hate to be that guy, but HELO/EHLO is smtp, not pop3