Note: Telnet is not completely plaintext and has control characters in the upper byte range (like 0xff or something, I forget).

Use nc or this TCP Bash technique if you really want to ensure decent compatibility when doing hacky solutions, otherwise a random 0xFF somewhere from a terminal console color change (or other control character) might really screw you over.

EDIT or ya know, use the correct tool like Curl.

I used telnet to send mail via SMTP once, it's quite literally a good social protocol because it begins with a polite 'HELO'.

Is it the reply to ‘HELO’ that enables things like tarpits?

Like if my server replied with ‘HI PLEASURE TO MEET YOU 127.0.0.1 THAT NAME SOUNDS FAMILIAR ARE YOU BY CHANCE FROM BOSTON MY MOTHER IS FROM BOSTON WELL QUINCY ACTUALLY BUT DO YOU KNOW 127.0.1.1 THEY ARE A REALLY GOOD FRIEND OF MINE YOU SHOULD MEET I HEAR THEIR DAUGHTER IS A DOCTOR DONTYAKNOW AND YOU COULD…”

etc, etc?

For SMTP tarpits you can do all kinds of fun stuff. Not just in the reply to helo. Like: always be slow to respond. Respond to each command with a temporary error. Accept everything, then pause, then error. Send back large chunks of garbage.

the '90s version of finding the hiring manager or boss on linkedin to try and get a job was connecting to the company's public smtp server with telnet, using their name to probe different email address patterns with "rcpt to:" (those days the actual servers were often directly connected to the internet and would leak email address validity in how they would respond to rcpt to) and then sending them a nice email.

smtp grew up to be an antisocial curmudgeon. extended smtp starts with EHLO.

> smtp grew up to be an antisocial curmudgeon. extended smtp starts with EHLO.

email will become so unusable, next one will have to be HELNO i guess

> smtp grew up to be an antisocial curmudgeon. extended smtp starts with EHLO.

"EHLO" still sounds friendly. It just sounds like a different accent or something. Know someone that used to answer calls with a friendly "Jello?".

Eventually Microsoft will debut Microsoft Extended SMTP which will greet with MEHLO

yeah, i think you're right. i originally read a bit of snarky blow-off, like "eh?" ... but you know, now that i think of it, it's actually does have more of a friendly canadian style vibe.

In the days of ultra thin containers, there's still no guarantee curl or wget will be installed, either.