smtp commands to test email between two servers via telnet

smtp-test

telnet smtp.example.com 25
    Trying 203.0.113.1...
    Connected to smtp.example.com.
    Escape character is '^]'.
    220 example.com running My Bitchin Mail Server 1.0.0
HELO example.org
    250 example.com hello example.org (198.51.100.1)
MAIL FROM:<[email protected]>
    250 2.1.5 sender OK
RCPT TO:<[email protected]>
    250 2.1.5 user [email protected] known
DATA
    354 send your message
To: [email protected]
Subject: This is a test.

Hear me now?
.
    250 2.6.0 message received OK
quit
    221 2.0.0 example.com closing connection
    Connection closed by foreign host.

The indented lines are the remote server's replies.