root@VM6:~# telnet mail.cogentco.com 25
Trying 149.127.109.12...
Connected to mail.cogentco.com.
Escape character is '^]'.
220 *************************************************************************************************
HELO
250 HHCSRV-MX08.ms.cogentco.com Hello [38.122.18.162]
mail from: freeload101@yahoo.com
250 2.1.0 Sender OK
rcpt to: freeload101@yahoo.com
550 5.7.1 Unable to relay