Quoting Brian Foster (blf at utvinternet.ie):
> as an FYI, there is also at least one site which will do
> a scan for being an open mail rely.
Aw, c'mon. It's dead simple to check without external assistance. All
you have to know is the definition of "mail relay" and a handful of SMTP
~ $ telnet linuxmafia.com smtp
Connected to linuxmafia.com.
Escape character is '^]'.
220 linuxmafia.com ESMTP Exim 4.22 #1 Mon, 08 Mar 2004 08:31:20 -0800 - mm9
250 linuxmafia.com Hello linuxmafia.com [18.104.22.168]
MAIL FROM: forgedaddress at aol.com
RCPT TO: victim at victimdomain.com
550 authentication required
221 linuxmafia.com closing connection
Connection closed by foreign host.
There ya go: My SMTP host tells attempted relayers to shove off (that 550
[A few minutes later:]
> telnet relay-test.mail-abuse.org
OK, I have to admit, Paul Vixie's script (which runs on that autoresponder)
_does_ try quite a few truly sneaky tricks in its attempts to find a way
to relay mail through your SMTP host. (I gather that one must be
telnetting from the SMTP host's command prompt. Spammers actually used
to use the former CGI implementation of mail-abuse.org's relay test to
_find open relays_.)
I'm happy to say that my SMTP servers are all sufficiently paranoid that
none of those tricks work.
Rick Moen Ban the Bomb.
rick at linuxmafia.com Save the world for conventional warfare.
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