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This is how email work(ed) over smtp. When each command was sent it would get a '200'-class message (success) or 400/500-class message (failure). Sound familiar

This is how email work(ed) over smtp. When each command was sent it would get a '200'-class message (success) or 400/500-class message (failure). Sound familiar? telnet smtp.mailserver.com 25 HELO MAIL FROM: me@foo.com RCPT TO: you@bar.com DATA blah blah blah how's it going? talk to you later! . QUIT

Telemakhos 9mo ago
This brings back some fun memories from the 1990s when this was exactly how we would send prank emails.
- fix4fun 9mo ago
  That was nice part of 1990s - many systems allow for funny things ;)
- kstrauser 9mo ago
  Yep! And also, if you included a blank line and then the headers for a new email in the bottom of your message, you could tell the server, hey, here comes another email for you to process! If you were typing into a feedback form powered by something from Matt’s Script Archive, there was about a 95% chance you could trivially get it to send out multiple emails to other parties for every one email sent to the site’s owner.
xg15 9mo ago
I like how SMTP was at least honest in calling it the "receipt to" address and not the "sender" address. Edit: wrong.
- 1718627440 9mo ago
  RCPT TO specifies the destination (recipient) address, the "sender" is what is written in MAIL FROM. However what most mail programs show as sender and recipient is neither, they rather show the headers contained in the message.
  - xg15 9mo ago
    Ah, sorry. You're right.
1718627440 9mo ago
For anyone who wants to try this against a modern server: openssl s_client -connect smtp.mailserver.com:smtps -crlf 220 smtp.mailserver.com ESMTP Postfix (Debian/GNU) EHLO example.com 250-smtp.mailserver.com 250-PIPELINING 250-SIZE 10240000 250-VRFY 250-ETRN 250-AUTH PLAIN LOGIN 250-ENHANCEDSTATUSCODES 250-8BITMIME 250-DSN 250-SMTPUTF8 250 CHUNKING MAIL FROM:me@example.com 250 2.1.0 Ok RCPT TO:postmaster 250 2.1.5 Ok DATA 354 End data with <CR><LF>.<CR><LF> Hi . 250 2.0.0 Ok: queued as BADA579CCB QUIT 221 2.0.0 Bye

Telemakhos 9mo ago

This brings back some fun memories from the 1990s when this was exactly how we would send prank emails.

fix4fun 9mo ago
That was nice part of 1990s - many systems allow for funny things ;)
kstrauser 9mo ago
Yep! And also, if you included a blank line and then the headers for a new email in the bottom of your message, you could tell the server, hey, here comes another email for you to process! If you were typing into a feedback form powered by something from Matt’s Script Archive, there was about a 95% chance you could trivially get it to send out multiple emails to other parties for every one email sent to the site’s owner.

xg15 9mo ago

I like how SMTP was at least honest in calling it the "receipt to" address and not the "sender" address. Edit: wrong.

1718627440 9mo ago
RCPT TO specifies the destination (recipient) address, the "sender" is what is written in MAIL FROM. However what most mail programs show as sender and recipient is neither, they rather show the headers contained in the message.
- xg15 9mo ago
  Ah, sorry. You're right.

1718627440 9mo ago

For anyone who wants to try this against a modern server: openssl s_client -connect smtp.mailserver.com:smtps -crlf 220 smtp.mailserver.com ESMTP Postfix (Debian/GNU) EHLO example.com 250-smtp.mailserver.com 250-PIPELINING 250-SIZE 10240000 250-VRFY 250-ETRN 250-AUTH PLAIN LOGIN 250-ENHANCEDSTATUSCODES 250-8BITMIME 250-DSN 250-SMTPUTF8 250 CHUNKING MAIL FROM:me@example.com 250 2.1.0 Ok RCPT TO:postmaster 250 2.1.5 Ok DATA 354 End data with <CR><LF>.<CR><LF> Hi . 250 2.0.0 Ok: queued as BADA579CCB QUIT 221 2.0.0 Bye