c tcp_connect localhost:1025

c <~ 220
c -> HELO localhost
c <~ 250
c -> MAIL FROM:<test@testy.com>
c <~ 250

c -> RCPT LALA: <>
c <- 500 unknown command

c -> RCPT TO:
c <~ 500

c -> RCPT TO:<pepe>
c <~ 501

c -> RCPT TO:<a@xn--->
c <- 501 malformed address (IDNA conversion failed)

c -> RCPT TO:<henryⅣ@testserver>
c <- 550 recipient invalid, please check the address for typos

c -> RCPT TO:<aaaa5aaaaXaaaa5aaaaXaaaa5aaaaXaaaa5aaaaXaaaa5aaaaXaaaa5aaaaXaaaa5aaaaXaaaa5aaaaXaaaa5aaaaXaaaa5aaaaXaaaa5aaaaXaaaa5aaaaXaaaa5aaaaXaaaa5aaaaXaaaa5aaaaX@bbbb5bbbbXbbbb5bbbbXbbbb5bbbbXbbbb5bbbbXbbbb5bbbbXbbbb5bbbbXbbbb5bbbbXbbbb5bbbbXbbbb5bbbbXbbbb5bbbbXbbbb5bbbbXbbbb5bbbbXbbbb5bbbbXbbbb5bbbbXbbbb5bbbbX>
c <- 501 address too long