We’ll be using telnet to connect to a mail server and send ourselves an email.
The parts in bold are the commands to enter.
[bob@linux ~]$ telnet mail.website.com 25
Connected to mail.website.com.
Escape character is '^]'.
220-mail.website.com ESMTP Exim 4.85 #2 Mon, 09 May 2022 22:12:59
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.
250 mail.website.com Hello domainto.sendfrom.com [192.168.1.2]
MAIL FROM: <firstname.lastname@example.org>
RCPT TO: <email@example.com>
354 Enter message, ending with "." on a line by itself
Subject: Test MessageThis is a test.
250 OK id=5a1g7i-1347MT-1p
221 mail.website.com closing connection
Connection closed by foreign host.
The first two “2, and 2,ab” mean that the message has not been read. The bottom 2 “2,S and s,Sab” mean that the message has been read or “seen?”. Guess that is what the S is for. Not sure what ab is for.