SMTP - Testing SMTP communication using telnet client

[Tested On]
Red Hat Enterprise Linux Server release 7.4 (Maipo)

Note: For Windows Server, please make sure telnet client is installed.

# telnet
open {mail-server} 25
EHLO {mail-server}
MAIL FROM:{sender}
RCPT TO:{recipient}
DATA
Subject: Test from SMTP Mail Relay
This is a test message
. (this is a dot)
QUIT

--- expected output ---
open {mail-server} 25
EHLO {mail-server}
-- output --

250-mail-server Hello mail-server [IP], pleased to meet you

250-ETRN

250-AUTH LOGIN CRAM-MD5 PLAIN

250-8BITMIME

250-ENHANCEDSTATUSCODES

250 SIZE
-- output --
MAIL FROM:{sender}
-- output --
250 2.1.0 Sender OK
-- output --
RCPT TO:{recipient}
-- output --
250 2.1.5 Recipient OK
-- output --
DATA
-- output --

Start mail input; end with <CLRF>.<CLRF>

-- output --

Subject: Test from SMTP Mail Relay

This is a test message
.

250 2.6.0 Ok, message saved

QUIT

221 2.0.0 See ya in cyberspace

Connection closed by foreign host.

--- expected output ---