telnetでSMTPを確認

トランザクションはこんな感じ。

# telnet 172.16.113.12 25
Trying 172.16.113.12...
Connected to 172.16.113.12 (172.30.113.12).
Escape character is '^]'.
220 localhost.localdomain ESMTP Sendmail 8.13.8/8.13.8; Tue, 23 Aug 2011 10:54:14 +0900
EHLO localhost
250-localhost.localdomain Hello [172.16.113.8], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE
250-DSN
250-ETRN
250-AUTH DIGEST-MD5 CRAM-MD5
250-DELIVERBY
250 HELP
MAIL FROM: canada@dev
250 2.1.0 canada@dev... Sender ok
RCPT TO: test@sys.jp
250 2.1.5 test@sys.jp... Recipient ok
DATA
354 Enter mail, end with "." on a line by itself
TEST
.
250 2.0.0 p7N1sEpb009113 Message accepted for delivery
QUIT
221 2.0.0 localhost.localdomain closing connection
Connection closed by foreign host.

 telnetでport25を指定して接続、EHLOコマンドでセッションを確立して、MAIL FROMとRCPT TOで送信元と宛先を指定、DATAコマンドで本文を書く。.（ドット）で本文終了。QUITでセッション切断。