[KLUG Members] Testing for open-relay.

[Peter Buxton]

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The simple way is to open a telnet session on the SMTP port, 25, and run
through the SMTP protocol:

> cares:02:28pm:~$ telnet killdevil.ath.cx 25
> Trying 64.108.72.56...
> Connected to adsl-64-108-72-56.dsl.gdrpmi.ameritech.net.
> Escape character is '^]'.
> 220 killdevil.ath.cx ESMTP Exim 3.35 #1 Wed, 26 Jun 2002 14:26:32 -0400
> ehlo caresswm.org

Here I identify my hostname, which reverse-lookups as cares.wmis.net,
which my home box, killdevil.ath.cx, notices (everything prefaced by a
number is from the remote MTA):

> 250-killdevil.ath.cx Hello cares.wmis.net [209.44.15.143]
> 250-SIZE
> 250-PIPELINING
> 250 HELP
> mail from: peter@caresswm.org
> 250 <peter@caresswm.org> is syntactically correct

No problem receiving my mail.

> rcpt to: bozo@hotmail.com
> 550 relaying to <bozo@hotmail.com> prohibited by administrator

But killdevil does not receive mail for any remote domains, either as a
mail drop or as a relay. Connection refused.

> quit
> 221 killdevil.ath.cx closing connection
> Connection closed by foreign host.
> cares:02:28pm:~$

AOL once scanned my box, or rather, submitted some relay mail. They had
4 or 5 addresses to run through to try and get it to relay. Wish I'd
kept it: they used the user%host.com@host2.com and all sorts of stuff.
(We passed with flying colors, of course.)

--=20
http://killdevil.ath.cx/~peter (/gpg.html)
OS/2? Hah. I've got Linux. What a cool name. -- l.torvalds

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