Пример SMTP-сессии

# telnet localhost 25
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 BBN-UNIX.ARPA Simple Mail Transfer Service Ready
HELO USC-ISIF.ARPA
250 BBN-UNIX.ARPA
MAIL FROM: Smith [at] USC-ISIF [dot] ARPA
250 OK
RCPT TO: Jones [at] BBN-UNIX [dot] ARPA
250 OK
RCPT TO: Green [at] BBN-UNIX [dot] ARPA
550 No such user here
RCPT TO: Brown [at] BBN-UNIX [dot] ARPA
250 OK
DATA
354 Start mail input; end with <CRLF>.<CRLF>
To: Jones [at] BBN-UNIX [dot] ARPA
From: Smith [at] USC-ISIF [dot] ARPA
Subject: Test

Hi!
This is a test message.
.
250 OK
QUIT
221 2.0.0 Bye
Connection closed by foreign host.