[user@example ~]$ telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.

<<< 220 example.com ESMTP Sendmail 8.14.4/8.14.4; Fri, 17 Jul 2015 20:29:26 +0200

helo localhost

<<< 250 example.com Hello localhost [127.0.0.1], pleased to meet you

MAIL FROM:me@localhost

<<< 250 2.1.0 me@localhost... Sender ok

RCPT TO:user@example.com

<<< 250 2.1.5 user@example.com... Recipient ok

RCPT TO:cc@example.com

<<< 250 2.1.5 cc@example.com... Recipient ok

RCPT TO:bcc@example.com

<<< 250 2.1.5 bcc@example.com... Recipient ok
data

<<< 354 Enter mail, end with "." on a line by itself


Subject: test
From: me@example.com
To: user@example.com
Cc: cc@example.com

this is an email message.
that has two lines.
.
<<< 250 2.0.0 t6HITQXA020072 Message accepted for delivery
quit