You type this text

Server should respond with this

TELNET mail.example.com 25

Trying 10.10.10.1.
Connected to mail.example.com.
Escape character is '^]'.
220 mail.example.com

HELO mail.example

250 OK

MAIL FROM:<sender@example.com>

250 OK - Mail from <sender@example.com>

RCPT TO:<youremail@outsideaddress.com>

550 Relaying is prohibited

QUIT

221 Closing connect, good bye

You type this text

Server should respond with this

TELNET mail.example.com 25

Trying 10.10.10.1.
Connected to mail.example.com.
Escape character is '^]'.
220 mail.example.com

HELO mail.example

250 OK

MAIL FROM:<sender@example.com>

250 OK - Mail from <sender@example.com>

RCPT TO:<youremail@outsideaddress.com>

250 OK

DATA

354 End data with <CR><LF><CR><LF>

From: sender@example.com
To: youremail@outsideaddress.com
Subject: Relay test

This is a relay test and only a test.
(type  <CR><LF>.<CR><LF> or [enter].[enter] to end data)

250 OK: Queued as T22122A5

QUIT

221 Closing connect, good bye