robster@light:~$ telnet 127.0.0.1 smtp
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
220 light.bluelinux.co.uk ESMTP Postfix (Debian/GNU)
HELO light.bluelinux.co.uk
250 light.bluelinux.co.uk
MAIL FROM: robster@bluelinux.co.uk
501 5.1.7 Bad sender address syntax