(0) jenner:~$ telnet mail.gmx.net 25
Trying 213.165.64.20...
Connected to mail.gmx.net.
Escape character is '^]'.
220 {mp009} GMX Mailservices ESMTP
HELO jenner
250 {mp009} GMX Mailservices
MAIL FROM: <me@there>
550 {mp009} Cannot resolve your domain
MAIL FROM: <me@jenner.cip.physik.uni-muenchen.de>
553 {mp009} Only registrated user are allowed to use this system
MAIL FROM: <wald.pepe@gmx.de>
551 {mp016} Need to authenticate via SMTP-AUTH-Login
quit