Esempio:

telnet smtp.marzorati.co 587
EHLO
auth login
incollare la username in formato base64
ZWRpc3BvcnRAdmgkZW8tbWFnYXppbmUuaXQ=
http://www.motobit.com/util/base64-decoder-encoder.asp
incollare la password sempre in formato base64
ZWRpc4BvcnQ=
mail from:
rcpt to:
data
From: sender@example.com
To: recipient@example.com
Subject: Test message
This is a test message.
.
QUIT
Se volete una GUI per Windows, potete usare TELNET25.exe