ns:~# telnet relay-test.mail-abuse.org
Trying 168.61.4.13...
Connected to cygnus.mail-abuse.org.
Escape character is '^]'.
Connecting to 217.167.207.58 ...
<<< 220 ESMTP Exim What do you want from me?
>>> HELO cygnus.mail-abuse.org
<<< 250 ns.mistral-habitat.fr Hello cygnus.mail-abuse.org [172.20.0.7]
:Relay test: #Quote test
>>> mail from: <spamtest@>
<<< 501 <spamtest@>: domain missing or malformed
>>> rset
<<< 250 Reset OK
:Relay test: #Test 1
>>> mail from: <nobody@mail-abuse.org>
<<< 250 <nobody@mail-abuse.org> is syntactically correct
>>> rcpt to: <nobody@mail-abuse.org>
<<< 550 relaying to <nobody@mail-abuse.org> prohibited by administrator (failed to find host name from IP address)
>>> rset
<<< 250 Reset OK
:Relay test: #Test 2
>>> mail from: <spamtest@maps1.pa.vix.com>
<<< 250 <spamtest@maps1.pa.vix.com> is syntactically correct
>>> rcpt to: <nobody@mail-abuse.org>

(it frezz)