c tcp_connect localhost:1025

c <~ 220

c -> DATA
c <- 503 5.5.1 Invisible customers are not welcome!

c -> HELO localhost
c <~ 250
c -> DATA
c <- 503 5.5.1 Sender not yet given

c -> MAIL FROM:<a@b>
c <~ 250
c -> RCPT TO: user@testserver
c <~ 250
c -> DATA
c <~ 354
c -> From: Mailer daemon <somewhere@horns.com>
c -> Subject: I've come to haunt you
c -> Bad header
c -> 
c -> Muahahahaha
c -> 
c -> 
c -> .
c <~ 554 5.6.0 Error parsing message

c -> QUIT
c <~ 221