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I guess you didn’t want my mail, then.

From a local ISP; I’m sure this seemed like a great idea at the time.

220 mx2.avalonworks.net ESMTP Postfix
helo hostname-of-internal-mailserver.mati.ca
250 mx2.avalonworks.net
mail from:<rich@mati.ca>
250 Ok
rcpt to:<test@igs.net>
554 <hostname-of-internal-mailserver.mati.ca>: Helo command rejected: Host not found

Er, sorry, what failed? I guess it forgot to tell me way back
then. I thought for a minute that it waited until RCPT to be able to
accept mail to postmaster in any case, but no, that fails there too.
I particularly like how an unsuccessful DNS lookup causes a permanent mail
failure, because DNS is always reliable.


Besides, no-one ever sends mail from a host that can’t receive mail
(say, behind NAT, maybe), and spammers would never put a resolvable
address in HELO.


On a hunch:

220 mx2.avalonworks.net ESMTP Postfix
helo mail2.igs.net
250 mx2.avalonworks.net
mail from:<rich@mati.ca>
250 Ok
rcpt to:<test@igs.net>
250 Ok

Yes, spammers would never ever just put the destination address
in the HELO. Sometimes I think antispam efforts exist to provoke
a cold war. (See also “challenge-response”).

Comments 2

  1. maes wrote:

    Those guys are such clowns… I deal with them in the role of implementation support for one of their suppliers and I’ve got to say I’ve been less than impressed with the tech team.

    Posted 17 May 2004 at 3:47 am
  2. fweebles wrote:

    Ugh, I had to use IGS for dial-up in Waterloo before DSL was readily available (like…5 years ago) and it was awful.

    Posted 17 May 2004 at 6:42 am