記一下，以免忘記..
本機測試 (xxxx 是怕被 bot 看到)
$ telnet localhost 25
Trying 127.0.0.1…
Connected to localhost.
Escape character is ‘^]’.
220 paar.xxxx.tw ESMTP Postfix
HELO uuh
250 paar.xxxx.tw
MAIL FROM: paar@paar.xxxx.tw
250 2.1.0 Ok
RCPT TO: paar@paar.xxxx.tw
250 2.1.5 Ok
DATA
354 End data with .
iufgaidusfgaiusdf
saoidhfasdiuhf
.
250 2.0.0 Ok: queued as 6C634F034
QUIT
221 2.0.0 Bye
Connection closed by foreign host.