%telnet localhost 25 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. 220 smtp.some.net ESMTP Postfix helo smtp.some.net 250 smtp.some.net mail from: sender@some.net 250 Ok rcpt to: noexistent@some.net 450 <noexistent@some.net>: User unknown in local recipient table quit 221 Bye Connection closed by foreign host.
ちなみに unknown_local_recipient_reject_code = 250 と強引なワザを使おうとしたら 450 Service unavailable が帰ってきた。